The original manuscript has a minor lacuna between with and heavy, enough for a word of the length the. However, the actual text is undoubtedly “with heavy taxes” and not “with the heavy taxes”. I would surmise that in the original manuscript Oliver Cowdery initially wrote “with the heavy taxes” in anticipation of the following “with the taxes”, then crossed out the intrusive the.
Summary: Maintain in Ether 10:5 the phrase “with heavy taxes”, the reading of the earliest extant source, the printer’s manuscript; although Oliver Cowdery seems to have initially written “with the heavy taxes” in the original manuscript, he very likely deleted the extra the.