Yes, it's important to scrutinize the receipt to see if the difference is due to a change in the base rate, one or more add-ons, or an increase in the taxes and fees. It could be multiple issues.

It may be tough to dispute add-ons that you agreed to by signing at the onset of the rental. No harm in trying though. The first step though is to understand the price breakdown and then develop a plan of action. We'd be happy to help analyze the charges if you post them in this thread once you receive your final receipt.