New shop in the works... Tax question came up

I have been working on a drop shipping store and after doing some research I realized I needed a state tax id and a EIN number for my LLC. I did all that.

My question is: I live in Pennsylvania and I know I have nexus here. Do I have to charge tax for all customers, or just the customers who live in Pennsylvania? I do not plan on orders from outside of the United States.

Any guidance is greatly appreciated.