Any convicted person, upon whom a fine has been imposed, may secure his release at the time of conviction or during service of sentence, by paying the fine imposed. Every convicted person shall be entitled to a pro rata deduction from his fine for any labor done or time served before payment. The fine so paid shall be delivered to the city clerk-treasurer. Nothing contained in this section shall prevent the discharge of any prisoner on account of illness duly certified by the city or Greenville County physician. (Prior code § 1-6-25)