I am no longer collecting sales tax, but I cannot figure out how to turn off the sales tax through paypal when clients finish their contract.

Are you referring to the tax on the payment integrations like Paypal? If yes, here's how to access it and to remove them in your payment form. http://www.jotform.com/help/296-How-to-Add-Tax-to-Your-Payment-Form

Also, if you have set up a tax and shipping within your Paypal account, this link will guide you through the process https://www.paypal.com/webapps/mpp/get-started/tax-and-shipping.

Let us know if you mean something else.