[8.2.0 php + postgresql] dealing with international provider tenders

Hello,
We buy services and goods worldwide and receive offers in different currencies even when buying localy (ex. for an antivirus solution, some ressellers made offers in € while others in tunsian dinar). Fixing a default currency for all transactions in ProjeQtor does not allow us to enter such amounts which get converted twice: when oppening the call for tenders offers, for comparison, and on the payment day if one of the ressellers which made offers in foreign currency had the least price.
How could we enter different currencies as they are received whithout conversion ?