SPOD has not started charging Sales Tax yet. We will inform all merchants via newsletter and the App once we know the start date.
We apply your sales tax rate based on your zip code. The tax rate is different in each state, and within each state, it varies by county, city, and district.
Usually sales tax is based on product + shipping cost, but there are exemptions.
Find more information on this question here: https://www.avalara.com/us/en/blog/2018/11/how-to-handle-sales-tax-on-shipping-a-state-by-state-guide.html