$1 overcharged

Hi,

Every time I buy iTune products (music & apps) from the iTune store, I have noticed on several occasions that there is a separate and additional charge of $1 debited from my credit card. Why am I charged an extra $1 for my purchases? Plus $1 charges don't show on my iTune purchase records. I find this strange.

I have always use the same credit card for all of my purchases and not sure why apple is charging me the extra $1.

Some clarification will be appreciated.

Thanks.