I'm guessing you're not in very good shape if you have trouble riding 5 miles, or you have some nasty hills. Tires without the knobs will reduce rolling friction, but if you can't ride 5 miles, you'll have to build up to it.

Go to your local bike shop (LBS) and tell them what you want to do, and ask them what they have. For 5 miles, I'd think a hybrid would be their choice to sell you. Test ride it for a couple miles. See if it has mounts for racks, so you can put your stuff in panniers (aka saddlebags).

If you have multiple LBSs in your area, repeat until you've found one you like. Buy it and ride it!