Basil Mramba, 75, and Daniel Yona, 74, both from the ruling Chama Cha Mapinduzi party, were in government when they issued the tax exemptions between 2002 and 2004.
"The accused acted arbitrarily in granting tax exemptions to a gold audit firm, totally disregarding advice by taxation and legal authorities," the judgement read.
The firm that received the exemptions was a subsidiary of UK-based Alex Stewart International.
Relatives wept as the sentence was read out in court in Tanzania's main city Dar es Salaam.
