I realize that cwinske already addressed your question, however, I uncovered some new code on a more recent post that may also be of interest to you (see https://cl.desmos.com/t/answer-that-is-a-fraction/1077 for more information). I was struggling to round values within a table and found the following code quite helpful:
rounded_value=numericValue(“\round(${value},2)”)
The code was helpful for me because it didn’t require simpleFunction.