Broker fees are added to the cost of a security when purchased and subtracted from the proceeds of the sale.
So 100 shares of stock purchased at $10/share, plus a $7.95 broker's fee would have a basis of $1,007.95. If the stock was sold at $15/share, minus a $7.95 broker's fee, the net proceeds would be recorded as $1,492.05. Virtually all 1099-Bs follow this process so there shouldn't be any need for you to make any additional entry for fees.