Decimal Format

[cogDev]

Hi,
I have a question about decimal places for my project
Users want to have a customized decimal format
If the number is less 10.00 then  number should be 9.00 format (2 decimal places)
If the number is between 10.00 and 99.00  then number should be 10.0 (1 decimal place)
If the number is over 100 then number should be 100 (0 decimal place)
With case statement and  round() I got all format correct but the only number ending with 0 or 00 after decimal gave just an integer. for example:  Original value 9.00 gives only 9  or 30.00 gives only 30 . So how do I place the decimal format where the original  number is 30.00 to 30.0 but NOT 30?
Thanks all in advanced.