Here is the best I've seen on kayak.com. There are lots of other airfare websites you should check as well before purchasing, as well as your favorite local travel agent.
The price is $458. I have not used Delta, but my understanding is that Delta includes Belize taxes as well as U.S. taxes (as with Continental but not American). Of course you should check this before purchasing, as all of the airlines change their terms regularly.
The NSU in-state tiuition waiver would defray about 2/3 of this cost. That is pretty cool!