Dear Concerned,
Yes if the Power of attorney is for specific purpose of selling the subject property only in that case the original of the POA can be given to the Buyer as there will be no need of this document to you once the property is sold. In such a case the demand of original document is valid.
Also if the power of attorney is referring to any other asset as well in such case you may keep the original but issue a true certified copy to the buyer.
Best of luck