There is an app commonly used in Italy that can be convenient. No need to find a pay machine or whether it's even working. You have your rego already entered so just confirm location and choose duration. If you return earlier, you can check in and refund the unused portion so there's no real fretting about duration either.

Having a consistent app throughout a solid amount of the country means you don't need to learn a new payment system interface in every new town, find out whether you can change language, is it tap or insert to pay, are there skimmers, etc.