I've never heard of a refund for registration fees, but if you decide to junk/sell the car instead of fixing it, I'm pretty sure you can save some money by transferring the plates to your new car, assuming you buy another car.

You didn't mention what makes you feel the car won't pass inspection, but hopefully you at least have some kind of idea of whether or not it's a car that's worth fixing if it fails inspection.

If you're unsure of your car's roadworthiness, and you're not mechanically inclined, you should probably pay a mechanic to check over the entire car before you invest in registration. You can go to the Registry (not your town hall), and get a 20-day temporary plate for about $10 so you can legally drive to and from the mechanic.

While driving an uninspected car isn't legal, if you do get stopped and cited for it, you're looking at a fine and some points on your driving record. Not ideal, but much better than driving around an unregistered car, which would get it towed away.