Read your state's sales tax laws and get back to me. I know for a fact that most states with a sales tax also place the burden on the consumer for paying the sales tax on out of state purchases. It may be called a use tax or consumption tax, but it's there. The burden is on the consumer, not the retailer, if the retailer has no physical location in your state.
Here is Idaho's, which is where I grew up, and I'm the most familiar with it. https://legislature.idaho.gov/statutesrules/idstat/Title63/T63CH36/SECT63-3621/. This shows where the burden falls. It explicitly states the burden is on the consumer of the goods, unless it falls on the retailer, and describes exactly when it falls on the retailer. Please note, the act of doing business in the state does not include out of state sellers shipping goods into the state and who have no physical presence or agents within the state.
Here's the definition of "Retailers engaging in business in this state" - https://legislature.idaho.gov/statutesrules/idstat/Title63/T63CH36/SECT63-3611/
As I said, you are living in the world of unicorns and lollipops if you think the consumer will pay a sales tax not included in the sale.