I honestly never even think of sales tax; I always just assume it's going to be added to the transaction (even though in PA certain things aren't taxed), and I couldn't even tell you when Amazon began collecting it. If I'm buying something, the additional 7% isn't going to change my mind or really affect how I view the transaction. I think the only time I really gave a shit was when I bought my car (because for whatever reason I wasn't anticipating sales tax would apply to a vehicle purchase).