It was always easy to keep a perfect running balance when the cashier can make change accurately and when there was a penny/nickel jar because customers might not have had exact change. It's only the normalization of sloppiness, or sometimes theft, of cashiers that causes shrinkage in reconciliation. It doesn't just magically happen and isn't a foregone conclusion.
It doesn't just magically happen, but it basically is a foregone conclusion. Nobody cares about a register that is off by 57 cents at the end of the day. You're going to waste WAY more money trying to hire "smart" cashiers at $5-$10 over the prevailing wage than you would just putting up with people who occasionally make errors in counting change.
Last time I worked retail was 1996-1997 and we meticulously had to count the register. If it was off then it was on us. This was pre touch screens and auto calculating registers. The same still applies in the latest modern world. You are off then you pay.