Would you consider it a reliable application to calculate the summed worth of coins by multiples of each coin weight?

I used to work in a casino where i'd count all the coins coming in from poker machines every morning. There was thousands of dollars worth and they'd be tipped into a huge pile, all the same denomination. I would shovel them into bags on scales as weighing them was pretty accurate. I think when they got to the bank and they put them through their counting machine it was out about $5 in about $30,000

Hmmm...errr..oh....can I phone a friend??

Not necessarily, in the US anyway the composition of coins has changed so the weights are different depending on the year.

Most banks rely on it