Taxes will be 14% VAT and a 45% import duty for anything containing Nicotine - Value below R400 (around $40 depending on the exchange rate) does not attract any taxes, you are only allowed to import up to 3 months' supply.
That is what the law says, but in reality it is pretty much a crap shoot, I've paid just VAT, VAT and import duty and nothing at all. On one case the stuff was seized. It all seems to depend on what the particular customs agents feels like on a particular day.