How to best approach rounding up decimals in C#

AFAIK, ToString( "0.##" ) will do, just increase number of # so that your value won't round up. E.g.:

decimal d = 1.999m;
string dStr = d.ToString("0.###");

This will generate "1,999" string (delimiter depends upon used culture).

As a result, you can use common very long formatting string: "0.############################" - to format all your values.

So trim the zeroes from the end.

decimal d = 1.999m;
string dStr = d.ToString().TrimEnd('0').TrimEnd('.');