Tipping is common practice in South Africa. Some guidelines concerning tipping are - in the bars and restaurants, the tipping is 10% minimum but preferably more.
The car parks are monitored by guards or watchmen, they will often ask if you want them to keep an eye on your car while you are away. If you accept - offer them a tip of R5 or more, according to the parking time.
In South Africa, the petrol station attendants will fill your car with petrol - they will also check your tyre pressure, oil-water levels and clean your windscreen. This typical South African service is around R5 or more at your discretion. Tipping is always welcome in South Africa.