How do I deal with Payment Gateway transaction fees?

How do I deal with Payment Gateway transaction fees?

I don't see any way to show a full transaction amount minus the bank transaction fees.

I use Venmo, Square, PayPal, and Stripe to accept money. All 4 gateways take a transaction fee. 

I need to figure out how to import the entire amount I received from the customer (pre fee) and then report a negative amount of the transaction fee so the imported total reflects the actual cash I received.

I checked the support docs and youtube/google, but I might no know the correct terms to type in, because I found nothing.

Here's an example: Customer purchases a $100 item. They pay $100. The payment gateway takes 2.9% + $0.10 per transaction. Therefore I am left with $97 cash that gets deposited into my bank account. I need to have the imported transaction show $100 was received but only $97 made it to my pocket, since an "expense" (potentially a COGS) happened instantly at the payment gateway. 

Any ideas?