Also prices outside of the big chain stores tend to be whole round numbers and cents are always divisible by 5. Prices listed always include the tax so if you are buying something and the price marked is €10.50, then that is what you pay. Some proprietors will also round down the total to your benefit to avoid odd change, for example a total of €8.05 will be rounded down to €8.00.
Petty cash does not seem to be a widely used concept in stores as many will not accept large bills, as low as a €20, early in the day. I have seen more than one proprietor turn away a sale when the customer used a bill that would require too much change returned. This is compounded by the fact that the bancomat or ATMs tend to disperse mostly €50 bills.
Cashiers are also quick to ask for il resto, or change, from you to round out what they give you back. For example if your total is €19.20 they will ask for 20 centessimi so they can give you back a €1 Euro coin.
There is also a small dish on every counter where you place your money and where in turn the clerk puts your receipt and change. Placing the money directly into their hand or into yours is not common. I have had some clerks give me a strange look when I tried to put money into their hand, though those who know me have no problems with this direct contact.