Yes, when conducting in-person transactions, it is possible to process payments using your in-house payment processing device, provided your payment processing provider allows the sale of raffle tickets.
From a RaffleTix platform perspective, these should be processed as In-Person Cash sales.
The recommended process, however, is to process all credit and debit card transactions through the Stripe payment processing platform built into the In-Person Sales page.
Alternatively, you can provide Buyers with a QR code. Buyers can scan the QR Code, which will take the Buyer to the raffle website, where they can purchase tickets on their own device via the Stripe payment processing service.