The official currency in Peru is the Nuevo Sol (S/.), which is divided into 100 Centimos. The currency includes coins for 5, 10, 20 and 50 Centimos and 1, 2 and 5 sol coins. There are bills in the denomination of 10, 20, 50, 100 and 200 Nuevos Soles.
The exchange rate for Soles to the USD is usually around 3. Prices are often quoted in Dollars but payment is expected in local currency, check the exchange rate they are giving you in this case.
Dollars can be exchanged in banks or in Casa de Cambio, but be aware that fake notes do circulate so choose carefully where you exchange money. No commission is charged on exchanges in Peru.
Peru is a cash society; it is very rare to be able to pay with cards of any type, except in large department stores and restaurants. Cash can be withdrawn from money machines in both dollars and soles from all the main banks in the cities (small towns will not have bank services). Only use ATM’s that are attached to a bank, not those on the streets or in shops.
Peru has IGV tax on all goods and services which is build into the price already