You pay what they said you'd pay.
No surprise card fees on the line, no "service charge" added at checkout, no rounding up. The number on your statement matches the number you agreed to. Refunds happen on the card you paid with, on the same day.
What that looks likeYou see "Heron Marina" on your statement, not "TWP-PROC-LDN". One line, one amount, one place.