Ah, yes. The Negotiator.

Having learned the arts of the silver tongue in negotiation and bartering, you gain the following benefits:

• If you choose not to convert a simple item (gem, chalice, figurine, etc) into gold upon finding it, you can attempt to sell it for 10 percent more than it is worth
• You gain advantage on Persuasion checks when attempting to get a higher or lower price on an item, provided to seller/buyer is at least neutral towards you
• During a lull in combat, you have advantage on a persuasion check that would cause fighting to come to a halt in favor of negotiation