Is a tip left in Italy? Yes or no? It is not necessary, but it is accepted if the service has been very good for you. If so, you must calculate 10% of the final rate, although I warn you that a third of Italians do not tip at any of their meals or drinks you take outside.
In Italy the cutlery is called covered and it is usually between two or three euros per head. It always exists, as soon as you sit in a chair in a restaurant, bar or cafeteria. You have to consider this. And beyond that, other restaurants add a post-sales service that which is in 10% of the account. It usually appears on the menu and may be charged at tables made up of many people, more than five. If you see that the service has been added to you, you do not need to leave a tip.
With respect to taxis it is common to round the final rate to reach a round number but that cannot be called a tip. If you hire the taxi in advance, it is not necessary to pay any extra or round up anything. Regarding the Guided tours are not an obligation either because they have a salary. Still if you want to tip 10% it is more than fine.
While tipping is not the norm in Italy, American tourists are not playing against their craze for tipping everywhere. Thus, in the most touristic places in Italy, many people expect to tip wherever you come from.