There's no laws to stop a private business from accepting cash or certain bills. I don't think the government can refuse it though.
Our pizza place doesn't take $100s because a) they don't keep the funds on hand to handle a lot of them most of the time and b) they got hit twice about two years ago when some fake money was circulating. I'm surprised it isn't more common here. Our banks close on Saturday at 1 for the weekend and there is literally no where else to get change after that (sometimes the casino will give it to you but only if they're slower than usual.) I hated, hated working on Sunday mornings at my old job because inevitably some asshole would come in and buy something under $5 to try and break their bill and if by some chance I did have the ability to take it, I'd give them back a bunch of $5s and they'd get pissed because it was inconveniencing them. BITCH YOU'RE INCONVENIENCING ME.