Whatever's cheap that you will want to ride the most. 5 miles is totally doable on any kind of bike, from a cruiser to carbon fiber racing bike.

I'm assuming since you're in college money is a concern...$600 is more than you would need to find a nice bike. Since it will likely get left outside for long stretches outside buildings, I'd maybe look for older used sport touring models. You can get something quite nice for a few hundred bucks that will look nice, classic, but not have a high bling factor for thieves, as well as do everything you want it to do.