Public restrooms do exist, but they're mostly poorly marked and difficult to spot, and many are crumbling and not up to Western standards of hygiene. Blue chemical toilets on the street have no washbasin, and toilets in train stations and other public buildings are often the squat type. Your best bet is to buy a snack in a café or bar and avail yourself of its facilities. With the exception of some restrooms in stores, you always have to pay to use the facilities, usually around 20R. The attendant sometimes has a dish for tips. It's also a good idea to carry a package of tissues with you into public restrooms.