Actually there's tax in all states.
Directly from Apple:
"Will I have to pay sales tax?
Yes. Because it has a physical presence in all 50 states, Apple is required by law to collect applicable sales tax on all orders from the Apple Store. Sales tax is also collected on downloadable software purchases if required by law in the jurisdiction where the purchaser resides.
What is the sales tax rate for my purchase?
The Apple Store applies the sales tax rate in effect at the time of purchase in the jurisdiction the purchase will be shipped to. (If that sales tax rate changes before the product is shipped, the new rate will apply.) The proof of purchase Apple mails you will include any applicable sales tax. If you place your order by phone, your Apple Store sales agent will provide you with the final total of your order, including tax and shipping charges."