Submit form without PayPal if total is $0

I have a registration form created in Creator that has several free and several paid choices. If a registrant's total is $0, how do I set the form to bypass PayPal to complete registration?

Here's a link to it: https://creator.zohopublic1.com/heather.hare/event-registration-hsg-2016/form-perma/HSG_2016/TvrjweWR219CJ9PWr6zO3HnVbtZE5CJhgQrq3GTm245p9FF2gJVUeBnE8A2A51YP3HBJZDYQBeV4DhzkG7rUJmtx2YyN6Urb8jzz