How much does this cost?

So we officially made it to Capetown late last night. We are all safe and sound, and except for the occasional muscle cramp from being confined to a plane for 16 hours and the relative lack of sleep I experienced for the same reasons I would say that I arrived in one piece. However, being in a new place even for just one day I have come to notice some major differences between here and Minnesota. Furthermore, I have already faced some struggles. I find that I am really struggling with the concept of money here. I cannot quickly convert my U.S. dollars to rands, and therefore cannot figure out how much things cost. I've noticed that my first reaction to this frustration is to simply spend the money and then take count later of what I've spent. This is an unhealthy approach because I think I will wind up spending way more than I had anticipated. I have also noticed how much I devalue the American  coin. When purchasing a cup of coffee in the United States, out of habit I usually toss all the coins that I am given back right into the tip jar. I did this in the airport in Joburg and received a song of gratitude from the guys behind the counter followed by the statement "You must be from America". I realized later that the coins I dropped in were likely equivelant to 2 to 3 US dollars... a rather high tip for a 3 to 4 dollar cup of coffee. I haven't even been here for a full 24 hours and my Americanisms are already showing. My goal is to take this lesson and to figure out ways that I can become more aware of my Americanisms and counter the ways in which they alter my experiences both here and back in the United States.