What is the name of the sound that a coin makes when hitting coins collected in a jar?

This can usually be called clink.

A light, sharp ringing sound, as of glass or metal.

It should be noted though that it isn't just limited to coins and, as such, can be used for multiple purposes. However, for what you describe, it could possibly be one of the better words.

For what it's worth, there's a sound-effect by the title clink of coins.

Along with "clink" there is also the word plink.

a short, sharp, metallic or ringing sound.

I feel, from my view, this is more closely associated with metal on metal contact sounds. I initially heard the word in the context of sport or leisure shooting, "plinking" is the act of going out and shooting steel targets or even small aluminum cans. A small "plink" sound is heard each time a target is hit. Though much lower pitched, this is the same type of sound when tossing coins in a jar.

My first thought was "chink", that's how I'd describe the initial sound of one coin hitting others in a jar if there was no further movement of either the new coin or the ones already there.

Sound of coin hitting the jar full of coins or other coins in the jar is called jingling. https://www.merriam-webster.com/dictionary/jingle

a light ringing sound that is made when metal objects hit each other.

It is obvious that coins are metal pieces.

Excerpt from wiki:

This design allowed coins to be put in the bottle but not allow them to be removed easily without the coins jingling against the glass. wiki: https://en.m.wikipedia.org/wiki/Street_performance

Note: it is not specifically related only to coins.