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So would you care to suggest what I should tip for this Limo service of €42? (where it states service incl). There will be just one pax - me, and I have one light carryon on rollers. </font>
We romans (and generally speaking italians, in Milan venice and other northern Italy cities may be slightly different) don't care too much for tipping...tips are not forbidden but I usually never tip anyone...Well it's up to you and to your willing of rewarding a very smooth service, but do not think of calculating and/or adding any percentage.
No one will come to your table asking if something had been going wrong if you didn't left 20% service on your restaurant bill: salaries are not based on tips...
Unfortunately, a lot of people (in hotel restaurants and maybe at limoservice) take undue advantage on tourists (mostly US citizen and Japanese) who don't know which tipping rules are effective in Italy...none!
Feel free to give one euro or two (maybe three at Limoservice: you may lend 45euro in notes without waiting for the change -50 it sounds to me a waste!-) or do not wait for your change if you really enjoyed what you had. You may even give the driver the exact change if you have it: he would be a little surprised due to your behaviour and while he was expecting something more but, as you told before, service is included! Do not bother at all....
BTW, In my honest opinion I do not feel limoservice is cheaper than a taxi, as someone (letiole, I think), stated above: a cab ride fare swaps between 30 and 40 but it ought to ask the driver before, to avoid bad surprises!
Enjoy Rome, you all!