I ask that because recently I've been to Rome and in two ocasions I saw the number 14 written as XIIII instead of XIV. One was in St. Peter Chapel in the "altar" were should be a statue of Pope Gregorio 14(written as XIIII) and the other one was in the numbers of the many entrances of the Coliseum, where we had again the XIIII following the XIII. I did some quick searches but could not find anything about it.
Yes, the "subtractive" format of iv, ix, xl, and so forth is by no means universal. Even in the later Middle Ages, as the infiltration of Arabic numerals into Latin Europe began to place a stronger emphasis on the location of a numeral in a number conveying meaning (in a strict tally system, XIX and XXI are the same--two 10s and a 1), they remained rare. Medieval sources are full of xiiii.
And by the late Middle Ages, the last i in a row is frequently written as j, so you'll see xij, viiij, and so on. Just to keep things interesting.