Well, you can!
After reading all the rules and regs posted by the "know it alls" here, I made a few calls and was told WHY I am able to do what I do and WHERE to find all the information.
There are $200, $800, & $1600 exemptions approved by CBP and they are based on where you have been on holiday and how you carry the booze in.
The Caribbean Basin is part of the "approved list".
I buy my 6 BOTTLES OF DOMINICAN RUM in the airport DUTY FREE and I keep the receipt. This is called "accompanied baggage" and is additional to my carry on that clears Dominican Customs before I reach the "sterile area" of the airport.
Before you go please read this CBP website on EXEMPTIONS
Types of Exemptions - CBP.gov
In brief:
$1,600 Exemption
If you travel to a U.S. insular possession
and to one or more of the Caribbean Basin or Andean countries listed above...(the DR is on this list)
"Similarly, you may include five liters of alcoholic beverages in your duty-free exemption" B]as long as one of the liters was produced in one of the countries listed above [/B](see section on Unaccompanied Purchases from Insular Possessions and Caribbean Basin or Andean Countries).[/I]
Just follow the rules posted on the CBP site, keep receipts and declare everything....you'll be fine.