Sue over less than $100? Even if you could, it wouldn't make sense, as you would only receive your damages, not a jackpot.
You can probably dispute the charges if they weren't properly displayed, but such charges for such sites tend to be unreasonable.
You may be able to dispute the charge entirely, if the site itself was illegal--I believe that visa & mastercard prohibit online gambling charges on their cards.
This is an example of where reading the fine print is key. You need to understand what you are signing up for when you put your credit card number in a website. This is especially true for shady businesses like online gaming. You may be able to dispute these charges, but read the fine print. You are talking about small enough numbers that it would not be worth a small claims suit. However, you can often get your money back by disputing the transaction through your VISA card.