You can see a fairly complete explanation of the Greek here: Matthew 5:26 ...Thou shalt by no means come out thence.
But to answer your question directly, we would say, “the last penny” today.
τὸν ἔσχατον (adj sg masc acc) "The uttermost" is from eschatos. In space, this means "furthest." In degree, it means "uttermost" and "highest." In persons, it means "lowest" and "meanest." Of time, it means "last" and "ending." It is usually translated as “last”.
κοδράντην. (noun sg masc acc) "Farthing" is from kodrantes, which is the Greek for the Latin quadrans, which means "one quarter of an assarion (a larger coin)." The quadrans was a bronze coin and the least valuable form of Roman currency. The equivalent today in America is a penny. A farthing was the smallest Brittish coin of the time, worth 1/4 of a cent.