I had difficulty with this problem as well. I code mainly in Actionscript 3.0 which is base coding for the Adobe Flash Platform, but there are simularities in the Languages:
The solution I came up with is the following:
//Code for Rounding to the nearest 0.05
var r:Number = Math.random() * 10; // NUMBER - Input Your Number here
var n:int = r * 10; // INTEGER - Shift Decimal 2 places to right
var f:int = Math.round(r * 10 - n) * 5;// INTEGER - Test 1 or 0 then convert to 5
var d:Number = (n + (f / 10)) / 10; // NUMBER - Re-assemble the number
trace("ORG No: " + r);
trace("NEW No: " + d);
Thats pretty much it. Note the use of 'Numbers' and 'Integers' and the way they are processed.
Good Luck!