I'm a bartender in Illinois and my credit card tips are added to my weekly paycheck. My employer takes a credit card fee out at 2.5% of my credit tips.
This is not really a tax question, but more of an employment law question, so you would get your best answer from an employment law attorney.
One thing you should do when you get your W-2 is make sure that your employer did not include in your wages the fees he kept for the credit card fees. If he did, you can request that he issues you a new W-2. If he is not willing to, then you can file a complaint with the IRS so you are not paying taxes on money you did not receive. Instruction on how to file a complaint are in this link. Call the IRS at 800-829-1040 or contact your local taxpayer advocate office to help with a complaint.
"My employer takes a credit card fee out at 2.5% of my credit tips."
That's sounds reasonable to me. They only get to keep 97.5% of the bar tab, because the credit card company gets the other 2.5%. The same should apply to you. It may be petty, but it's reasonable and probably legal (I'm not a lawyer). They only received 97.5% of the tip, but you want them to pay you 100%.