According to my wife the lawyer, if you buy something over the Internet from a company which has a business presence in your state (not county), then you have to pay sales tax. Land's End sells through Sears and as far as I know there is a Sears in every single state. But if I something over the Internet from a company which does NOT have a business presence in my state, sales tax isn't charged.
HOWEVER! If your state charges sales tax and you have purchased stuff over the Internet from companies which do not have a business presence in your state, you must declare how much sales tax you would have paid on the stuff and remit said amount to the state.
Example: I buy a wiffler from Best Wifflers over the Internet. Best Wifflers has an outlet in my state, so I have to pay the state sales tax. I also buy a nixerler from New York Nixerlers, which only has offices and stores in New Jersey -- I don't pay sales tax (unless there is some sort of compact between New Jersey and my state) but I'm required to tell my state that I spent $4,534,985.12 on the nixerler and remit to my state the appropriate sales tax.
Since we are all good citizens I'm sure that we all do this.