It's designed to be an invisable tax to the consumer - so as long as you pay the advertised price and nobody tries to add 10% tax on at the end, it is legit from your point of view. Some people decide to tell you their prices includes tax others don't bother to mention it, the end result is the same.
Opposite to the system I have found in the US where you see a price tag, think that's the cost and then get whooped for a bunch more on the bill ot the till!!!
Seems a better system to me.