Yes, you should tell them, I would, cause they WILL find out somehow, may as well tell them by yourself so they have trust in you to tell the truth. But if they find out another way, first of all, they may be more angry at you and have less trust, second, depending on the parents, you might get in less trouble than them finding out in a different way.
I truly think you should at least TRY to quit, because it gets expensive and even harder to quit as you go, but I won't nag on you.