Is it bad to close a credit card?

I got a credit card from the place I bought my tires from that had 6 months with no interest. I paid it off before 6 months so I have zero balance.

I was just going to cancel it. Is it bad for my credit to do so? I know your credit score is calculated on how much credit vs. how much debt.

What should I do? I would never need to use this card again.