most fish can jump out of the tank. If you have coverglass it will limit the number that make it out.
Fish usually only jump out if they are startled, if something is trying to eat them or if the water quality is really bad.
Be sure to check your hood at the back for holes where wires go through, cover them with sponge, i had a swordtail just out of one and die, that was even with a condensation lid on..