Using a credit card for purchases less than $1

It seems that I'm always given weird looks by store clerks and friends when I pay for an inexpensive item (something less than a dollar or so) with a credit card. I understand, of course, that the store owner may have to pay a flat fee + % on the transaction, but I doubt the clerk knows or cares about that.
To me, using a card on these types of small transactions makes perfect sense from the consumers' perspective. Here are some advantages:

1. I don't have to get back a handful of coins.
2. It slightly reduces the purchase price (via cash back bonuses).
3. I don't have to go to the ATM constantly. ($100 in cash can last me months!)
4. Keeping all of my daily purchases on the same card can help answer the question, "Where did all of my money go?"

That being said, this only makes sense if you are paying off your "daily spending" card at the end of every month. If you aren't doing that, you're probably better off paying cash.