Concise Bible Dictionary:

“658. The Assarius” From Manners and Customs of the Bible:

‘Aσσάριον is one of the two words rendered “farthing” in our version.
It was the Roman as or assarius, a copper coin, equal in value to a tenth of a denarius, (see note on Matt. 20:22And when he had agreed with the laborers for a penny a day, he sent them into his vineyard. (Matthew 20:2), #683) or three farthings English, or one cent and a half American.
In Luke 12:66Are not five sparrows sold for two farthings, and not one of them is forgotten before God? (Luke 12:6), two assaria are spoken of. It is thought that a single coin is there intended of the value of two assaria. The Vulgate has dipondius. Madden says: “It is very clear from the fact of the word dupondius, or dipondius, which was equal to two asses, and was a coin of itself, being substituted for the two assaria of the Greek text, that a single coin is intended by this latter expression. This idea is fully borne out by the coins of Chios. The Greek autonomous copper coins of this place have inscribed upon them the words ACCAPION, ACCAPIA ΔΨΩ or ΔΨΟ and ACCAPIA TPIA” (History of Jewish Coinage, p. 243).

“742. Mite Farthing” From Manners and Customs of the Bible:

1. The λεπτόν, or “mite,” was the smallest Greek copper coin. Its value was the eighth part of an assarion; thus making it worth about one fifth of one cent, or three eighths of one farthing. See note on Matthew 10:2929Are not two sparrows sold for a farthing? and one of them shall not fall on the ground without your Father. (Matthew 10:29) (#658). It is also mentioned in Luke 12:5959I tell thee, thou shalt not depart thence, till thou hast paid the very last mite. (Luke 12:59).
2. The κοδρύντης, or “farthing,” was the smallest Roman brass coin, and was worth the fourth part of an assarion, and equal to two lepta, or mites; that is, about two fifths of one cent, or three fourths of one farthing. It is also mentioned in Matthew 5:2626Verily I say unto thee, Thou shalt by no means come out thence, till thou hast paid the uttermost farthing. (Matthew 5:26).