Use System.Math.Round to rounds a decimal value to a specified number of fractional digits.
var pay = 200 + bonus;
pay = System.Math.Round(pay, 2);
Console.WriteLine(pay);
MSDN References:
- http://msdn.microsoft.com/en-us/library/system.math.round.aspx
- http://msdn.microsoft.com/en-us/library/zy06z30k.aspx