The broker basically resets the positions and provides either a credit or debit for the interest rate differential between the two currencies in the pairs being held. The trade carries on and the trader doesn't need to deliver or settle the transaction. When the trade is closed the trader realizes their profit or loss based on their original transaction price and the price they closed the trade at. The rollover credits or debits could either add to this gain or detract from it.
Most brokers also provide leverage. Many brokers in the U.S. provide leverage up to 50:1. Let's assume our trader uses 10:1 leverage on this transaction. If using 10:1 leverage the trader is not required to have $5,000 in their account, even though they are trading $5,000 worth of currency. They only need $500. As long as they have $500 and 10:1 leverage they can trade $5,000 worth of currency. If they utilize 20:1 leverage, they only need $250 in their account (because $250 * 20 = $5,000).
I enrolled in Robots coarse$297 +trend trade bundle$27. I felt that the Finch robot was worth it. As I have paid people to build me a equivalent robot which has cost me $300. After purchase a few weeks goes bye and Robots coarse is advertised for $97 limited time. (urgh) I assumed after watching all his you-tube videos about the Finch robot, that it is profitable and assumed it was hands free (%100 Automated) but just like most trades or Robots there must be intervening to get the robot out of bad trades. I see some hope with the robot but its money is mostly made bye the bad trades when you need to add trades to average out all trades to break even or make money if you can stomach the stress to get your %5-%15 draw down back to profit. It worries me that this might just be another short lived marketing tool, and this honeymoon Finch style robot dies out, and something different will be advertised for sale.