Depends on the shop, bro, but you can tell by how much they charge for the hourly fee up-front. If they take around $60 up-front for the hour, that means the tip is not included. In that case you ask for extras in the room with the girl directly. You can do this at the beginning or near the end of the session, it's up to you.
If they take more than $100 for the hour, then the NHJ is included, and you can ask for more extras (and pay more for it!) in the room. Note that this only applies to erotic massage parlours, NOT actual remedial massage parlours! Those can charge more than $100 /hour just for remedial massage (hot stone, etc).
Shops I know of that take the tips up-front are SBM, 227 Broadway, and the Korean shops.
Other shops like SS, Diva, are tip-in-room type.