My father had a grudge against some utility back in the late 70's, and they sent him a bill mid-month for $4, some overage, or miscalculation on their part that was the last straw as far as he was concerned.
So he sent in a check for $2 The next bill came for $2, and he sent in $1. When the bill came in for $1, he sent in $.50.
At $.25 someone from the utility billing dept. called him up to ask what the problem was.
He was having a tough time deciding to send in $.12 or round up to $.13 the next time round... So he vented to the caller and felt better.