Nick here from Shopify.
Great question. In this instance though, you would need to set up the tax location in your store admin manually for each location you want to sell in. There would be no other way for Shopify to know exactly where you are. We have a helpful guide going through this in a lot more detail and how to set up POS tax rates the right way for your store.
Hope this helps and clears this up for you more. Don’t hesitate should you have any other questions about anything.
All the best,