I as well in the past have recieved a penny refund from DL.
It was rather funny actually, I was flying BizElite to Istanbul and upon my return I had a flight to ATL that I wanted to change to give me more time to clear immigration/customs/security. So upon checking in the in BizElite area I asked the ticket agent if he could adjust my JFK-ATL flight on the return. He did some typing and started to laugh. I asked what was so funny and he said that DL owed me a penny.
He then printed me out my refund reciept and looked at it for a minute showed it his friend and then said, well Mr. Dan1431 I thought I had seen it all working at this job but this is a totally new one to me.
Dan