This is something that I deal with as a caterer. There are two different ways to go about this, but I think the best way to go about it is to add a 2nd location. With this option you will be able to add a different tax rate without messing with the tax rate at your current location. You will just have to enable the tax rate for the location and disable the other. Hope this helps!
To set up a separate location, go to your dashboard, click on "Account & Settings," click on "Locations."
