It's not our fault that the states have been very shoddy at this sort of enforcement since the dawn of online purchasing, which has been ongoing for like 10-15 years now.
9-10% is something I would love to pay now since I have to deal with 5% GST (federal tax) PLUS 8.5% TVQ (Quebec sale tax) on top of the total after GST. So, the combined taxes are at 13.925%, not 13.5%. Oh sod off Quebec. Then if you go to Europe, it's not too hard to find countries with 20% -/+ sale taxes, but they're already included in the price and not calculated at the register. I wonder for a long time why the US and Canada cannot include them in the price (apart from alcohol and gas) so I don't have to figure out if I should pay a bit more or not on some goods. It would save us a bit of time and it would tell us what we should have the right to know before going to the cash... knowing the final price. And saving me some trouble saying "sorry, darn... I'm missing a nickel".
Oh yeah, I know why... it would make goods look "more expensive", something the retailers would be so opposed, so that's why sale taxes aren't included in the prices here and in the States. But what's the point? It would be a bit more expensive anyways at the cash. A retarded logic.