Code:
   Private Sub CalculateToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles CalculateToolStripMenuItem.Click
        'declare all constants and variables
        Dim coupon As Decimal = 0.1 'discount codes
        Dim customer As Decimal = 0.15 'discount codes
        Dim nodisc As Decimal = 0
        Dim coupcode As Decimal
        Dim toppingtotal As Decimal
        Dim sales As Decimal = 0.08 'sales tax
        Dim pepp As Decimal = 0.75 'each topping seperate to simplify adding, for me
        Dim onoin As Decimal = 0.75
        Dim cheese As Decimal = 0.75
        Dim couptotal As Decimal
        Dim dapizza As Decimal
        Dim total As Decimal
        Dim fintotal As Decimal
        Dim pizzaArrayDecimal(,) As Decimal = {{5.99, 6.99, 7.99, 8.99},
                                                {6.99, 7.99, 8.99, 9.99}} 'declare the array
        'this else/if is to output errors in case customer information boxes are empty
        If namebox.Text = "" Then
            MessageBox.Show("Error. Missing information.")
        ElseIf streetbox.Text = "" Then
            MessageBox.Show("Error. Missing information.")
        ElseIf citybox.Text = "" Then
            MessageBox.Show("Error. Missing information.")
        ElseIf statebox.Text = "" Then
            MessageBox.Show("Error. Missing information.")
        ElseIf zipbox.Text = "" Then
            MessageBox.Show("Error. Missing information.")
        End If

        If none.Checked Then
            coupcode = nodisc
        ElseIf tennoff.Checked Then
            coupcode = coupon
        ElseIf prefcus.Checked Then
            coupcode = customer
        End If

        If peppers.Checked = True Then 'adds peppers to cost if applicable
            toppingtotal += pepp
        End If

        If onions.Checked = True Then 'adds onions to cost if applicable
            toppingtotal += onoin
        End If

        If xcheese.Checked = True Then 'adds extra cheese to cost if applicable
            toppingtotal += cheese
        End If

        If sizebox.SelectedIndex = -1 Then  'error code if no size is chosen
            MessageBox.Show("Please choose a pizza size.")
            Exit Sub 'exits instead of continuing calculation
        End If

        If crustbox.SelectedIndex = -1 Then 'error code if no crust is chosen
            MessageBox.Show("Please choose a crust style.")
            Exit Sub 'exits instead of continuing calculation
        End If

        If sizebox.Text = "Small" Then  'if else to associate cost array with what crust and size pizza
            If crustbox.Text = "Regular" Then 'small regular
                pizzabox.Text = pizzaArrayDecimal(0, 0)
                dapizza = pizzaArrayDecimal(0, 0)
            ElseIf crustbox.Text = "Stuffed Crust" Then 'small stuffed crust
                pizzabox.Text = pizzaArrayDecimal(1, 0)
                dapizza = pizzaArrayDecimal(1, 0)
            End If
        ElseIf sizebox.Text = "Medium" Then
            If crustbox.Text = "Regular" Then 'medium regular
                pizzabox.Text = pizzaArrayDecimal(1, 0)
                dapizza = pizzaArrayDecimal(1, 0)
            ElseIf crustbox.Text = "Stuffed Crust" Then 'medium stuffed crust
                pizzabox.Text = pizzaArrayDecimal(1, 1)
                dapizza = pizzaArrayDecimal(1, 1)
            End If
        ElseIf sizebox.Text = "Large" Then
            If crustbox.Text = "Regular" Then 'large regular
                pizzabox.Text = pizzaArrayDecimal(0, 2)
                dapizza = pizzaArrayDecimal(0, 2)
            ElseIf crustbox.Text = "Stuffed Crust" Then 'large stuffed crust
                pizzabox.Text = pizzaArrayDecimal(1, 2)
                dapizza = pizzaArrayDecimal(1, 2)
            End If
        ElseIf sizebox.Text = "Monster" Then
            If crustbox.Text = "Regular" Then 'monster regular
                pizzabox.Text = pizzaArrayDecimal(0, 3)
                dapizza = pizzaArrayDecimal(0, 3) '
            ElseIf crustbox.Text = "Stuffed Crust" Then 'monster stuffed crust
                pizzabox.Text = pizzaArrayDecimal(1, 3)
                dapizza = pizzaArrayDecimal(1, 3)
            End If
        End If

        discountbox.Text = String.Format("{0:n2}", couptotal) 'output discount 
        toppingsbox.Text = String.Format("{0:n2}", toppingtotal) 'output toppings total
        couptotal = (toppingtotal + dapizza) * coupcode 'calculate discount
        total = (toppingtotal + dapizza - couptotal) * sales 'calculate sales tax total
        fintotal = toppingtotal + dapizza - couptotal + total 'calculate final total
        totalbox.Text = String.Format("{0:n2}", fintotal) 'output final total
        taxbox.Text = String.Format("{0:n2}", total) 'output sales tax 
    End Sub
So, I have the code above. The problem I'm having is calculating the discount using radio buttons none, prefcus, and tennoff. If one is chosen, it will default to one of the constant discount options defined in my variables, then used to calculate and output at the bottom of my code. No matter what I choose, it outputs the discount to 0.00. The code works great except for this and has everything I need it to have, this is only the calculate as this is the only part that refers to the radio buttons and outputs.

Any help would be much appreciated. I've redone the radio button parts countless times, and stared at it for at least an hour, to no avail.