The general principle is that a Muslim may work in lawful employment, and a cashier position is, in itself, a permissible occupation.

The fact that customers use different methods of payment, including credit cards, does not automatically make the cashier’s work impermissible. The cashier is not the one issuing the loan, charging interest, calculating interest, or entering into a ribā contract. Rather, he is processing the sale of a lawful product and receiving payment through a commonly accepted payment network.

For this reason, many contemporary scholars distinguish between:

Direct participation in a ribā transaction, such as writing, structuring, approving, or servicing an interest-bearing loan, and indirect interactions that merely occur within a society where interest-based financial systems exist.

A cashier in a grocery store, retail store, restaurant, pharmacy, or similar business is generally not considered to be assisting in ribā merely because a customer chooses to pay with a credit card.

However, the ruling can differ if the employee’s duties directly involve promoting, selling, opening, or processing interest-bearing financial products. For example:

• opening credit card accounts,
• marketing interest-bearing loans,
• processing loan applications,
• or working directly in the administration of interest-based financing.

These situations are much more problematic because they involve direct facilitation of ribā contracts.

Therefore, if your role is simply that of a cashier accepting various forms of payment for lawful goods or services, the stronger contemporary opinion is that this work is permissible and is not considered unlawful cooperation in sin.

Allah says: “And cooperate in righteousness and piety, and do not cooperate in sin and transgression.” (Al-Mā’idah 5:2)

The cooperation prohibited by this verse is direct and meaningful assistance in the sinful act itself. Merely accepting payment for a lawful sale from a customer who chooses a particular payment method does not normally fall into that category.

Accordingly, a cashier’s job in an otherwise lawful business is generally permissible, even when customers use credit cards or other mixed forms of payment.