I know a fair few people who work in shops, hospitality, and similar. Being a dick to your server is still being a dick to your server, even if you dress it up as doing it to get at their employer.

Occasionally your server deserves a bit of dickish behaviour because of their attitude, but this is relatively rather rare in my experience.

The company has an almost immeasurably small impact on their profits, and will never be measured anyway.

The cashier is a real human doing a job to put food on the table and has done nothing to deserve it, and may well have been far more hurt by the head office than you.