You swipe physical cards.
I'd note that a lot of
Best Buy gift card deals are for eGift cards, so you'd just present the barcodes to the cashier to scan and the cashier will need the 4-digit PIN to type into the register.
What I do is, before I go into a store, I'll open the link to each eGift card on my phone, then take a screenshot of each eGift card, which goes into a photo album. When I'm in line at checkout, I'll open up my Shopkicks app to the QR code, and I'll open up my photo album to the screenshots of the eGift cards. When the cashier asks if I have a Best Buy Rewards number, I'll say no (even though I do, because you don't earn Rewards points on purchases paid for with gift cards), but say I have this, then present the Shopkicks QR code for the cashier to scan so you can earn kicks towards more gift cards. Then when the cashier rings up the total amount, I'll say I also have these, and present the cashier with the first of my eGC screenshots for him to scan the barcode, then read the PIN to him to help speed up the process, then swipe my phone to the next screenshot and tell the cashier I have a few more, and repeat. In store, I believe the registers can handle up to 10 or 15 gift cards, certificates, savings codes.