The subscription plugin now has support for the Stripe Pricing Table and Stripe Checkout
which allows for the proper tax collecting.
https://github.com/discourse/discourse-subscriptions/commit/45754baa0070f1fe600f4fd71d2d46e61d359b13
Once you setup your pricing table in stripe you can configure these settings in Discourse:
to start using Stripe Checkout for you subscribe page.
As part of the pricing table setup there is an option to enable automatic tax collecting
