Charges that can't be explained

The car had PLENTY of dings and scratches, many of which I had to point out when picking the car up. They don't have unlimited mileage on our car rental, and we only found out about this after we picked up the car. When we returned the car, we had to wait about 40 minutes in line, thankfully we got to the airport early. We were happy to pay the charges, but when we received the receipt and asked our service person, they kept giving us vague answers that didn't make sense. We then went into the manager's office who then proceeded to say that in Italy, there are taxes on taxes. Okay? What does that mean? He wouldn't go on to explain any more. Just beware of hidden charges at Hertz, Dollar and the rest of the fleet, just another typical car rental shop that sends you hidden charges upon return of a vehicle.