Is a Visa required?

A tourist card is included with your flight.  It's good for 30 days. Then you either extend up to a total of 120 days OR simply pay an overstay fine on exit.  It's the same fee as extending but it's much easier.

Thank you appreciate your speedy reply.

I just got back from a little over 3 month stay.  I always just pay the fee at the airport.   3-9 months is 5600 DOP, so if you're gonna be there expect each person to pay 5600 pesos when you're at the airport leaving. 

About $95 USD per person?

Departure fee In Pesos or Dollars? Or does it matter?

I always pay in pesos, not sure if they take dollars.   Just come prepared with pesos.  This was also at Santiago STI Airport. 

They do accept dollars and credit cards normally.

what would an overstay of say 6 days cost for 2 persons departing from POP?

@delmerbmartin  From the current fee chart, it would be $3,500 RD each, up to 90 days.

That would be counted as 36 days