When using the ShopTill-e ePOS you can easily accept split tenders/mixed card, cash etc payments.
When a customer is ready to complete their transaction simply click the 'pay' button in the ePOS system as usual. In the receive payment screen enter a reduced tender amount into the 'Tendered' field and click the relevant tender type for that 'part' payment e.g. cash the system will register this and then display the balance due after taking account of the part payment.
You can keep adding part payments using the different tender types until the whole sum is paid at which point the order is completed in the usual way and the split payment are show against the order.