Sales tax is not included within the product costs that are visible during the product creation process or on https://www.spreadshop.com/products/. As tax varies by state, city, or even district, the sales tax is always added on top of the product costs after an order is made.
Sales tax can only be calculated after the order has been placed with Spreadconnect and therefore it is only visible on the order detail page and the invoice.
For some states, the merchant can provide Spreadconnect with a Resale Certificate that will enable Spreadconnect to drop the sales tax charge.