jQuery validationEngine and tabbing system

Question

I am working with the jQuery ValidationEngine and also have a custom tabbing function that includes a registration form on one of the tabs. I can't get the tabbing to stop from going to the next step if there was an error on the form.

Here is my code:

var formValid = $('#registerForm').validationEngine({returnIsValid: true});
if(!formValid) return false;

The above is supposed to stop the tabbing system from working but its not... any ideas on what I am doing wrong?

validationEngine Link