Rabbits do sleep, but it's rare to catch them at it because they're very light sleepers and will usually wake up at the slightest sound or change in smell/light. I've seen some of my rabbits sleeping during the hotter hours of the afternoon (I usually think they're dead at first because they're so relaxed and on their sides). I've also seen them take quick naps while they have their legs tucked underneath them (this is usually how they sleep during the winter that I've seen). They can sleep with their eyes open, at least as far as I can tell.
Rabbits are technically nocturnal, so they would be expected to sleep more during the day than at night, but being prey animals, they never let their guard down.