I think it is worse than that, RSRH. The can belongs to the state. That is why you pay $0.05 for it. You get it back if you return it. He should return the cans but not take the $0.05.
In general, regarding Ta’os Akum, let’s remember that it is not Mentchlich either way. The Sefer Chasidim says that you won’t see a Siman Bracha (a blessing of success) from such money. Non Jewish people don’t have the Torah and yet you expect them to behave in a civil manner. You should live up to the same thing, Mechuyav or not.