Yes, but you won't get extra points if you don't perform better than your last try. So like, you can improve your score, but you can't grind the same level over and over to farm cash and XP. An example: You start out by completing a level with a score of 1700. You decide to try again, and score 2100 this time. In this case, you'll end up with 2100 points from the level, but if you were to try a third time and score 1500, then that is the number that will be used. This also means that you could get in trouble later if you perform badly, but rest assured that the game can be completed by an average player. Near the end of the game, you'd have most available upgrades purchased on an average playthrough, and even more on an exceptionally good one. I'm not aiming towards days of grinding gameplay, but rather an hour or two of smooth and intense gameplay that keeps you on your toes.
According to my calculations, the current levels will take around 72 seconds each to run through, and with 20 levels, that adds up to 24 minutes of gameplay. A bit underwhelming actually. Might have to do more levels in light of this, or perhaps make later levels longer. Some levels will probably be replayed, either because of death or wanting a higher score.