The central bank of zimbabwe scrapped the country's national currency on friday and started using the u.s. dollar the zimbabwean dollar has for the past decade become more and more worthless because at an incredible 500 billion percent in 2008.since in the u.s. dollar. economists estimate to exchange their remaining local currency for the u.s.dollar. the official exchange rate is one u.s. dollars. The official exchange is one u.s. dollars. That's 35 followed by 15 zeroes