If your QuickBooks Payment account links to QuickBooks Online, your payment transaction will automatically downloaded under Chart of Accounts. Thus, you'll have to check what type of expense account you used to tag for the processing fee and then run a quick report to view these fees.
Here's how:
Go to the Left panel, select transactions, and choose Chart of Accounts.
Find the Expense account type.
Select Run report in the Action column or View register dropdown list.
You can also access your Merchant Services Center to view the specific fees by going to the Activity & Reports menu and selecting Fees. You can choose Print or Export the data to see a summary of all the fees. Check this article for further details: Find transactions, deposits, or fees.