I'm never sure about this, so I'm asking the advice of wait staff and/or restaurant owners...
Say my tab is $100, and I'm going to tip $20 on it. I'm paying with a credit card, but I have cash for the tip.
Is it better if I...
(A) Pay the entire $120 with the credit card.
(B) Put $110 on the credit card, and leave a $10 bill separately.
(C) Pay the $100 on the credit card, and leave a $20 bill separately.
Or does it make no difference to you at all?