As I'm grading math tests for MS Math, Algebra 1 and Geometry today, I just wanted to let you know how I grade in case you want to do the same. I always grade the test and give a grade with partial credit for partially right answers (always -1 for failing to label). And then I let my kids fix any problems for half credit back.
Obviously you can do it however you would like, but this seems to give incentive for understanding what they got wrong which is so important!