I mean, I get the change thing only because I've had too many interactions that start out with my total being something odd, like $4.36. I'll give the cashier a $5 bill plus 14¢ in change ($5.14) and they'll get confused as to why I did that and go "oh, no, the $5 is enough."

Like, I know it's enough but I don't want a shittonne more change in my wallet/pockets when I already have these spare nickels and pennies, so please take what I gave you and just ring it in then give me my nice round 50¢ back. I gave you 6 coins so that in the end I'd get 2 coins back instead of 64¢ worth, which would be 7 coins minimum - in addition to the 14 spare cents I had already.

If you can't do the math, that's fine, but just punch in what I gave you and the register will do it for you.

/rant.