Rounding or Modulus

[Master Shake]

I have had only one programming class a long time ago and am in over my head (Shake is pretty dumb.) All I want to do is round down to the nearest 0.25 increment.

Say my number is 1879.92 (closer to 1880 than 1879.75), I would like a value of 1879.75 returned.
If the number is 1764.27, I would like 1764.25 returned.

I think modulus only works for returning whole numbers.

Is there an easier way than using a nested if statement like?

double price;
double roundedprice;
double remainder;

//price is calculated earlier in another section of code

roundedprice = Round(price);
remainder = price - roundedprice;

if (remainder >= 0.75) { price = roundedprice + 0.75 }
if (remainder >= 0.50) { price = roundedprice + 0.50 }

if (remainder >= 0.25) { price = roundedprice + 0.25 }

if (remainder >= 0.00) { price = roundedprice + 0.00 }

Any thoughts?

The actual part of code that I am trying to insert this into follows:

            // Condition set 1
            if (DefaultInput[0] > ChandelierSAR(5, 3.5).Chandelier[0]
                && ToTime(Time[0]) > ToTime(8, 30, 0)
                && ToTime(Time[0]) < ToTime(15, 0, 0))
            {
                EnterShortStopLimit(DefaultQuantity, ChandelierSAR(5, 3.5).Chandelier[0], ChandelierSAR(5, 3.5).Chandelier[0], "");
                Alert("MyAlert0", Priority.High, "", "", 1, Color.White, Color.Black);
            }

            // Condition set 2
            if (DefaultInput[0] < ChandelierSAR(5, 3.5).Chandelier[0]
                && ToTime(Time[0]) > ToTime(8, 30, 0)
                && ToTime(Time[0]) < ToTime(15, 0, 0))
            {
                ExitShortStopLimit(ChandelierSAR(5, 3.5).Chandelier[0], ChandelierSAR(5, 3.5).Chandelier[0], "", "");
            }