That depends on the implementation. E.g. Sam's Club lets you scan items as you put them into your cart and just walk past the registers.
In the local grocery store at rush hour, cashier lines are long and self-checkout tends to be quicker for buying 3 items. Taking a whole cart into self-checkout is slower than a cashier, because the self-checkout has like a 5% chance per item of going into "assistance needed" mode.
In the local grocery store at rush hour, cashier lines are long and self-checkout tends to be quicker for buying 3 items. Taking a whole cart into self-checkout is slower than a cashier, because the self-checkout has like a 5% chance per item of going into "assistance needed" mode.