Matthew 22:19

They brought unto him a penny - A denarius: probably the ordinary capitation tax, though the poll tax in the law, Exodus 30:13, Exodus 30:14, was half a shekel, about twice as much as the denarius. The Roman denarius had the emperor's image with a proper legend stamped on one side of it. It was not therefore the sacred shekel which was to be paid for the repairs of the temple which was now demanded, but the regular tribute required by the Roman government.

The tribute-money - The money in which the tribute was paid.

This was a Roman coin. The tribute for the temple service was paid in the Jewish shekel; that for the Roman government in foreign coin. Their having that coin about them, and using it, was proof that they themselves held it lawful to pay the tribute; and their pretensions, therefore, were mere hypocrisy.

A penny - A Roman denarius, worth about 14 cents equals 7d (circa 1880's).