This script is OnChange, and will automatically round the selected field to [x] value. The script can either be applied to a Catalog Item, or a specific Variable in a Var Set.

For example, if prompting a user for a cost, and said cost should only be in multiples of $5.

Any instance of [VAR NAME] in these files should be replaced with the name of the variable that the script is being applied to.

More information and a full write-up available on Community.