Could you specify what anime you watched, or do you have a picture? It would help a lot.

Based on the description, the scenes in question are referencing the habit to bind together Mon copper coins with a stick or cord in uniform amounts. This photo shows a bunch gathered together that matches the description. Both Japanese and Chinese coinage had square holes in the center of the coins to aid the finishing process during the coins' casting. This also proved convenient for merchants and other travelers who could bound coins together in roughly standardized measurement units. Western accounts from the nineteenth century describe this practice and this Japan Times Q & A piece gives some of the history of the square holed coinage.