As a cashier at the checkout, being addressed as Madame, "Yes Madame", what do you think about that?

It depends on the emphasis and situation.

In general, I do not find it personally appropriate and somewhat unpleasant, so did not want to be addressed – neither at the checkout nor elsewhere. Also find it uncommon when you say, “Yes, the lady” or “Yes, the Lord”- earlier submissive nowadays mostly ironic. Or gracious lady…..a bit very much from time, including: “Yes, Madame”

In my region, “Madame” is often spoken ironically. Like, for example, Oh the madame is too fine for ….”

At the checkout of my favorite supermarket sit very nice people who always kindly sell me the things without such a non-temporal address 😉🌞🌞🌞

Bonne nuit

🌝😺