How to compute taxes for offline transactions

Hello, let's say you finally have all of your paper work together for your seller's permit. There are some websites that in order for you to do business with them or buy from them, you would need your license. You then buy the merchandise but what if someone or people in your city want to buy offline from you as well, how would you add tax or how would you report this sale?

Your tax obligations remain the same no matter if you are selling online or offline, there is no difference between to two modes.