Am I Jew, am I Jew?

I have developed a habit unconsciously lately that disturbs me,

When I put fuel in the car I have been not stopping on the exact amount and have been putting 1 cent more in, because of the rounding of prices I am not charged for the extra cent as I pay with cash for my fuel purchases.

I used to mock those who did such a thing and thought of them as stingy bastards, perhaps I have now become one?

I have a black dog at my heels lately.