If the material is relatively new to you, I would check your answers as you go along.
It’s important that you learn how to work through the problems correctly early on. You don’t want to do the entire homework one way only to check the answers, see that you were wrong, and have to somehow forget what you had already practiced and relearn how to it the correct way.
If you have already practiced several problems and you’re now studying for a test, wait until you’re completely finished to check your answers.
I’ve realized that it’s impractical to study for a test, particularly in mathematics, with the answers you need within reach. On the actual test, you won’t have the satisfaction or reaffirmation of checking your answers, so why should you use it while you’re studying? Get used to not being able to check your answers immediately and you’ll be much well-prepared for your test.
As both a teacher and a student, I find it more productive to check the answer of each problem immediately rather than at the end of a series. It’s better to have immediate feedback because it builds confidence and because the problems in one set are often related. That way, you learn immediately if you are on the right track.
If you’re not absolutely confident of the approach you took, then check the answers right away. If you’re confident that you understand the process, the algorithm and the principles … then move on to the next one.
Moving on when you lack confidence will impede your progress because part of your mind will be worried about the previous problem. If you stop to check after every problem, even when you’re comfortable with the problem conceptually it’s likely to lead to boredom and get you bogged in the details. (Yes, you may have made careless mistakes and that’s fine to catch later. But you want to flow through the challenges and save the more routine tedium for later (after a break and rewarding yourself).