If you have products that don't have tax or that have tax rates that differ from the general tax rate set in Settings > Billing it's a simple process to set this up.
You can set variable tax rates on a case-by-case basis for products, memberships and membership add-ons. You can't do this for ad hoc charges as these will take the general tax rate set.
To change the tax rate, head over to the item that you would like change the tax rate for and select Edit. You'll then be able to override the general tax rate. You'll see the suggested tax rate, ghosted in light grey, which based on the general tax rate, but you're free to change it to whatever you need it to be. Then hit save and you're done.
You can repeat this process for any other products or plans that have different tax rates in Habu.