Give the exact change when you can in Switzerland, it’s how things are done here. I noticed this when I went to the store and I gave flat bills when I had change on me and the cashier demanded the change to make it exact. Of course this was done without me really understanding the words, as I have not gotten the hang of Swiss German, yet.
The take away from this experience and others having observed the checkout line, is to take your time. No one will bother you, it is more of a courtesy and good manner to operate in this way here.