This is a regular verb. It follows the conjugation pattern of the verb falar.
Present:
O governo tributa produtos importados.
The government taxes imported products.
Preterite:
O estado tributou esses bens fortemente.
The state taxed those goods heavily.
Conditional:
Eles tributariam mais esse setor.
Eles tributariam mais esse sector.
They would tax that sector more.