Dear Dour Bank Teller,
I apologize profusely that the roll of quarters that your co-worker gave me in exchange for a crisp $10 bill mere moments ago contained a surprise penny among the expected coins. Although I was heartily amused to find that a hobo penny had jumped the quarter train and, when discovered among the quarters in my palm, desperately hoped to escape notice by putting on its best George Washington voice and trying with all its might to appear less ruddy-faced, I had to rectify the situation at once. This is the sort of "small stuff" that I am told not to "sweat", but you must realize that I have always regarded that expression with a delightful hint of bile.
So, I apologize for bringing this to your attention with a gentle and patient smile. I apologize for offering you the imposter quarter a/k/a the penny to exchange for the quarter that was due me and not assuming it was a bonus gift. I apologize for handling this with humor and calm, when clearly it was a situation that demanded silent surliness, which you so brilliantly demonstrated upon the presentation of a replacement quarter along with a thorough lack of an apology for any inconvenience.
Had I only known the protocol expected in a situation such as this, I surely would have wiped the hobo penny on my own bum (the body part variety, not the unemployed drunkard I store in one of my kitchen cabinets) before handing it to you. But as it was, I only did what I thought made sense.
Yours in proper Presidential coinage,