ELECTRONIC FINANCIAL TRANSACTION PROCESSING APPARATUS, NAMELY, AN ELECTRONIC DATA TERMINAL AND ASSOCIATED FIRMWARE AND OPERATING SOFTWARE FOR USE THEREWITH FOR ASSISTING IN THE PROCESSING OF FINANCIAL TRANSACTIONS BETWEEN A MERCHANT AND A CUSTOMER BY INTERFACING WITH EXISTING PERIPHERAL DEVICES, SUCH AS ELECTRONIC CASH REGISTERS; SUCH AS TRANSACTIONS INCLUDING POINT-OF-SALE TRANSACTIONS, BANK TELLER TRANSACTIONS, LOYALTY TRANSACTIONS, AND INVENTORY AND STOCK TAKING TRANSACTIONS