A user in one of my LinkedIn groups had an unusual requirement.  He needed to eliminate trailing zeros from a series of decimal numbers.  The numbers could go out to 4 or more decimal places and he didn’t want to show any trailing zeros.  He wanted a column to look like this:

1.2345
2.345
3.45
4.3

instead of this

1.2345
2.3450
3.4500
4.3000

There are other approaches but I think this is the simplest. Just put your field in the first line of this formula:

Local NumberVar x := {YourField};
Local NumberVar y := Length (Totext (Truncate (Val (StrReverse (Totext (x,9)))),0,''));
Totext (x,y)

Note that this will work with numbers up to 9 decimals. You can increase the number of decimals in the second line by replacing the number 9 with a larger number.

The above example is a formula that returns a string. Another approach is to take the original numeric field and go into:
[ Format >> Field >> Number tab >> Customize button ]
Then put the following line into the condition button of the decimal places property. You don’t even need the name of the field:

Length (Totext (Truncate (Val (StrReverse (Totext (CurrentFieldValue,9)))),0,''))

 This is simpler because it doesn’t involve writing a formula field and it also doesn’t change the data type to ‘string’.  It can also be applied to any field without modification. The only downside is that having the logic hidden in a conditional property may mean that it is forgotten.