With few exceptions, sales tax applies to the gross receipts received or gross selling price received from the sale of products or taxable services. The specific definition will vary by state but, for example, Georgia sales tax law defines the term “sales price” to be the selling price of the product less any “ discounts, including cash, term, or coupons that are not reimbursed by a third party that are allowed by a seller and taken by a purchaser on a sale.”
In layman’s terms, that means if the original price of something you sell was $100, but you offer a 50% discount, then the taxable price is $50.

Hope this helps.