jQuery validate - need a new method

jQuery validate - need a new method

I need a method that checks that values in all fields of certain class are all increments of 10.
I've looked at additional-methods.js but the ones there rely on regex or too complicated for my needs so I'm frustrated about the syntax.
Basically all that needs to be checked is that value of the field (of certain class or id) satisfies this condition:
(value % 10)==0
and if not error message is given.
I think highlighting of the field(s) is taken care of in the main validate.js.