Can I add sales tax to an auto loan?

I'm looking to get a loan, most likely from a dealership, for a used car. I still owe about $5,000 on the car I have now, and I'll be trading it in. It's not very reliable and my insurance is sky high because it's considered a sports car. Anyway, the only way I can make this happen is if I can take enough out to cover the sales tax, also. Do car dealerships do this often? I'm still exploring my options, if I can find a co-signer I can go with a bank loan, my credit score is just under 650. Also, I live in Missouri, if that helps. Any thoughts are appreciated!