Can my employer take off money on my final check if I use sick days/vacation days during my two weeks notice?

Currently I have accumulated a lot of sick/vacation/personal days off. I made the decision to quit and next week will be my final. However, I know they won't pay me for all those days of PTO unused. I was planning to play sick for a majority of my final week so that I can use my hard earned PTO. But I was told they can just take whatever I used out of my final check. Is this true? I mean what if I really was sick? Anyone have experience in this?