Punta Cana then means Higuey municipality. I believe you could also marry in San Rafael de Yuma (on the way to Boca de Yuma).
Go to
Comprometidos con la Verdad! - Junta Central Electoral.
then click on Tasas para los Actos del Estado Civil for the cost. It says RD$5,000 when one of those getting married is a Dominican and the marriage is carried out at the Civil Registry Office.
Then at Oficialias for the address.