Looks more like a Rojo or maybe a High color mini - too much color for a Dwarf Cav.

are the back sides of the leaf red or green? it could be a sumatrana X gran nain cross, a zebrina if it has red leaf backs.

This is most likely a cavendish type banana, the most common banana-plant in the trade. I have recently heard there is a dwarf cavendish-type, that has been selected for the indoor housplant market, tolerating lower light levels. If you bought it at home depot or similar large chain, chances are this could be it.

I have seen this striking black colour on many young dwarf cavendish specimens. The plant tends to go all green as it gets older/bigger. In fact, many banana-plant cultivars do the same thing, such as musa sikkimensis. When sikkimensis leaves exceed 6 feet long, they tend to be all green.

The link is from "The Musacea", and shows a nursery growing ornamental Dwarf Cavendish.

Here is a link that might be useful: Commercial production of Dwarf Cavendish as Houseplants

I think pitangadiego and mrbungalow have it right, looks like a hi color cavendish but could be just a young one that will grow out of it's color. Check out this pic www.agristarts.com/mu_hicolor.jpg
The underneath is green not red. I got it at a regular greenhouse, but it was promoted as an ornamental. I love it no matter what. I hope that it bears fruit someday, since my Basjoo won't.
Thanks everyone!!!

That's good news for you if your banana leaves are green on the backside, and you're wanting fruit.
Most of the zebrinas and their cousins that produce non-edible bananas have red backs. So you have something most likely edible.