Allowable Litter

What are you allowed to litter? Cigarette butts used to be but not anymore. I dropped a receipt yesterday and it blew right away. I wasn't going to chase that but I suppose I should have done. Money? In Japan you pick everything up, even the smallest coin but that's more a matter of respect for money than littering. Here, I don't stoop for a penny so is that littering? What about a fiver? If I just let them go is that littering? What about an Ipod or a car or a child? Oh God I think I've been littering all the time. What about a breath or an aura? It could make you worry about your social niceity.