It seems it's not so much the database here that matters, but the transaction software and the interfaces you need. Can people pay with creditcard or Paypal or checks, do they earn vouchers when they buy something in your shop, what can they do with their vouchers, do they need to be able to login into their account, what rules for privacy, what rules from the financial authorities, your bookkeeping software, etc.

Without such requirements specified in enough detail nobody can tell what you need.