Does anyone have cash register experience?

• can you get cash from a visa gift card
• cash secured credit card
• credit card machine

I work at a retail store as a cashier and someone came through with a 140 dollar order. He swiped his card and entered his pin and I accidentally hit the rebate button. It said enter slip and hit enter so I put a random slip into the machine because there was no way to get out of it. The order totaled and the drawer opened which isn't supposed to happen since he paid with a card. I assumed it was opened for me to put the slip in but now I'm worried that it was meant for money and he never got charged? Can someone please help and tell me what the rebate/traveler button on a cash machine does? thank you!

Additional Details

POS?

I work at Meijer if that helps, it's the registers they use there.

Does anyone have cash register experience?