An electric shear will cut light guage stainless but will curl the edge slightly.
The trim Charlie mentioned would hide that.

If you wanted to keep the sheet flat w/o trim you could plasma cut but it would require finish grinding the edge and then buffing out any discoloration. If the sheet is thin it may warp very slightly form the heat if the cutting is done too slowly.

I like to cut shapes on our corner notcher as it leaves the sheet nice and flat w/o edge curling.