You can exchange your currency at any of our local banks; at Hato International Airport, there is a branch of Maduro & Curiel's bank near the arrivals hall (exit the hall to your left and go left again). Banks usually close at 3:30 PM but the airport branch is open until 6 PM. You will be required to show a valid ID to be able to exchange money.
Your hotel's front desk may also be able to exchange small amounts of USD or EUR for you.