Legal Question in Business Law in Illinois

If you mean the store has a performance standard requiring its cashiers to get at least one patron to sign up for a store credit card during each shift, and the standard is applicable to all such employees (or such other class of employees as the employer has set up) it is very possibly legal. Different jobs have different performance standards - in car dealerships for example if you don't sell X number of units in a given time period, that could be grounds for termination. But there are other considerations and you have given too little information to be really helpful. It would be best for you to talk with an attorney who can ask you additional questions that could give a clearer picture of the whole thing and maybe find a way to invalidate the requirement. Then again sometimes the supervisor may just not be explaining the requirement and it may be worthwhile to clarify it with him/her or ask for his/her supervisor to clarify it. Beware, however, that unless you are protected by a collective bargaining agreement (union) or some kind of employee manual with grievance procedures or other established employee-employer rules and procedures, Illinois is an "at will" employment state and you can be terminated at any time for any or NO reason, just as you would have the same right to quit.