Online retailers rarely include tax in the USA unless their warehouse or place of business is located there. E.g. Newegg has warehouses in CA and PA so they charge sales tax for any packages shipped to people inside those states. But they don't charge sales tax to say MD. This is becaause there are way to many variations in sales tax across states so until the Federal government steps in or states really push like NY did. Though even in the state example what online retailers just do is not charge sales tax and tell whoever is buying it in that state to buy the sales tax. Which rarely the buyer will ever do.