Some of the best hair styles for round faces would be you always want to balance a shape. If you have something that's very round you want to add height to it and you want to keep the sides very, very minimal.
One thing that I definitely would consider is ask yourself if you really do have a round face. Maybe ask some of your girlfriends. Most women think that they have a round face and most do not. So try to get a true accurate picture before you choose a hair style that would go along with that.
Most of the time we say keep it really smooth on the sides, really tight on the sides and then add a little bit of height to the top. That should balance and elongate your face.
You might also want to consider keeping part of your hair down so that instead of seeing that full circle you kind of cut off those two sides so you get an elongated look. Also maybe a long ponytail or something that was actually long within the hairstyle would be very, very beautiful.
So in general, I would say keep it a little higher on the top and a little smoother on the sides. That'll really help to balance out a round face.