Oh No!!!!!!!!!!!!!!!!!!!
Well, for one, it would be a waste of money. Even if you could learn Japanese from it, it's way over priced. You can go download the thing, and all the Japanese lessons that are out for it. You're bad at this
Though you could get it for free, I would still go with what YuriYuri said. That's the best place I know of for Japanese grammar. There's much more resources for learning Japanese that you can find here, and they'll all help you learn more than Rosetta Stone will.