Perhaps you can use the Round function in an auto-enter calculation that checks a global preferences field to determine whether to round values to 2 or 0 decimal places? and the same expression can include a calc that adds any needed trailing zeroes after the decimal place. The global field (or a global variable) can be loaded from a preferences table when the file opens.
But use it for display. Rounding values at the wrong tims can introduce small cumulative errors into your data if the rounded values are used in calculations where unrounded values should be used instead.