From deposit to payout the money stays in dinars, with no conversion on the way. However many names the cashier lists, the groups are three: bank routes, vouchers with counters, and the shops themselves.
The amount that lands is the same; what each method asks of you is not. The bank route depends on your bank letting that kind of transaction through, a voucher asks for no card at all, and the counter asks only for the trip to a payment point.
The differences show on the withdrawal side, and one step decides the rest: verification. Before the first payout a Serbian-licensed operator has to check who you are, because the law says so, and done early it takes a few minutes, while left until later it can take a whole weekend.