I'm not sure from your question what you are actually looking for. Storage and Display are two separate things.
STORAGE
If you want to store a number with a fixed precision in SQL SERVER use DECIMAL
CREATE TABLE MyTable
(
MyNumber DECIMAL(5,2)
)
The above will store 5 digits, 3 before the decimal point, and two after.
Here's the documentation: http://msdn.microsoft.com/en-gb/library/ms187746.aspx
If you are storing currency values, then there is the MONEY datatype too: http://msdn.microsoft.com/en-us/library/ms179882.aspx
DISPLAY
If you are more interested in the display of values rather than the storage (You've already mentioned they are floats in the database) then in your C# application you can use something like this:
string display = string.Format("{0:0.00}", myNumber);
Here's the documentation for custom formatting of numbers into strings: http://msdn.microsoft.com/en-gb/library/0c899ak8.aspx