kaso

One root, two everyday senses, and they are the same idea. A kaso is the physical place where money is taken in a shop, the till or cash desk, and it is also the fund an organisation keeps: la kaso de la klubo, la kaso de la societo. English splits those into two words. Esperanto does not need to, because both are the box the money sits in, and the box is what the root actually means.

Three near neighbours, and only one of them is a container.Kesto is a chest or crate, the wooden thing in the corner: same job, no money implied. Kaso is specifically the money box, and by extension the counter it stands on. And kazo is a different word altogether, with z: a case in the grammatical, legal or medical sense, from Latin casus, a falling-out of events. Kaso never means a case in that sense, and kazo never holds anything. One letter, two Latin roots, no overlap.

In use. The person at the till is a kasisto, the machine is a kasregistrilo, and a savings bank in the older phrase is a ŝparkaso. Enkasigi is to take money in, which is what a business does at the end of a day. If you want the bank as an institution rather than the drawer, that is banko.