Multiple Banks with Vendor Masters

In a case where the users have two banks on the vendor master , how does the system know which bank to choose, or does it always take the first one ?

Going on from that if they had two banks in say Germany but one was to be used for Euro payments the other for USD payments... Is there any possibility of building something into the vendor master to indicate these currencies so that the system will choose automatically ?

Thank You,

Suresh