The Tourist Tax is what we call in the jargon, an imponderable.
It is collected by the city from all hoteliers for each reservation made, whether you are a foreign or "local" tourist.
The amount is fixed and varies depending on the hotel category. Therefore, you will be required to pay it directly to the hotel upon check-in.
You now know everything, but we strongly advise against bringing it up in a conversation. 😉