How Exchange Rates Work. Maybe you've traveled to Mexico or Canada, and exchanged your American dollars for pesos or Canadian dollars. Or, perhaps you've traveled from England to Japan and exchanged your English pounds for yen. If so, you have experienced exchange rates in action. Here, the government pegs its own currency to one of the major world currencies, such as the American dollar or the euro, and sets a firm exchange rate between the two denominations. To preserve the local exchange rate, the nation’s central bank either buys or sells the currency to which it is pegged.