You can always use bike baskets that goes on your rack. Your commute is only a few miles, so it should suffice. Some people in the cycling community might consider it too "gay" but I prefer it. Makes my bike looks like an actual commuter/utility bike. I also can't justify spending alot of money for bike specific "paniers" or bags that looks so ugly, IMO , but the Chrome messenger bags do look a bit cool.

Oh yeah, don't forget to use the bungee cords to keep the stuff from flying away.