checkout counter; cashier's desk
The counter or desk where you pay in a store, restaurant, or similar establishment.
Please pay at the checkout counter when you finish shopping.
The cashier's desk at that shop is always crowded.
会計 refers to the act of paying or the bill, not the physical counter. 勘定台 is the physical place where payment happens.
Compound of 勘定 (かんじょう, 'calculation, bill') and 台 (だい, 'stand, counter').