Is it permissible to work as a cashier in a store that adds a fraction of a dirham (more than 0.60) to the full dirham when calculating the price of an item for the customer, under the pretext that fractional denominations are not available?

It is not permissible for a store to take a small portion of a customer's money without their knowledge and consent, such as not returning the remaining change (fractions of currency). This falls under the category of unlawfully consuming people's wealth, as Allah Almighty says: (O you who have believed, do not consume one another's properties unjustly, but only [in lawful] trade by mutual consent from among you), and as the Prophet, peace and blessings be upon him, said: (The property of a Muslim is not lawful except with his willing consent), and (All of a Muslim is sacred to another Muslim: his blood, his wealth, and his honor), and his saying, peace and blessings be upon him: (Whoever wrongfully takes the right of a Muslim by his oath, Allah has made Hellfire obligatory for him and Paradise forbidden for him), even if it is a small amount.

If the store does not have the exact change, it should offer an alternative (e.g., candy), or give the customer the option to donate it. The customer must be informed of this; if they agree, then there is no harm, otherwise it is forbidden to take it.