Not sure about where you're at, but it's a rarity to come across a register that doesn't have a customer facing display, with at the very least, the total you are being charged for your goods and/or services.

Many small shops have a separate credit card terminal where they enter the amount to be charged.

From a cursory google image search it looks like you're right, I suppose my routine skews towards merchants that don't have one of those.

On a per store basis it's extremely rare since only bigger stores have that.