Zimbabwe legalised the use of foreign currencies as legal tender, thus negating the need for the inflation-ravaged Zimbabwe Dollar, which has now been withdrawn from circulation.
The US dollar is now the de facto currency in Zimbabwe, although the South African rand and the euro are also widely accepted. Do not expect to be given change if the value is less than $1 as there are no coins in circulation, in supermarkets, you may be given change in chewing gum or sweets!
The use of credit cards is still very limited, with only a few service providers accepting VISA or MasterCards cards in Zimbabwe. Also, ATM use can be very limited for non-citizens, so please do yourself a favour and come with plenty of cash on hand.
As for costs, non-imported things are very cheap especially labour intensive things, however for a tourist drinking coke and eating pizza, prices are not that much lower than in South Africa. Petrol gasoline supplies are improving, so are food supplies in supermarkets.
Haggling for a better price is common, but keep in mind that most people are very poor.