As posters said, you can buy on e-bay without problems.
But, if your question is selling on e-bay from the DR, here is how you do it. E-bay now has e-bay stores that will handle your goods for you. It never needs to hit the shores of the Dominican Republic, except when you ship it out. So, you find the e-bay store that wants to handle your goods, for a percentage of course. Then, you ship from the DR a container load, to your 'store' at best shipping prices.
(Make sure that you have your information well researched. And of course, you need to visit your 'store' and have your ducks in a row! This is like another business, don't enter into it, if you've not done your homework. It takes time and money to set this up and it takes time, focus and money to make it work. Certain items have trouble with getting into North America - Don't try this with avocados for instance :ermm

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Now you can go ahead and sell on e-bay and ship from the location of your 'store' at usual US shipping rates.
So, there you go! Let me add, you need to have a US side business presence established.