I rememeber being shocked a few years ago when I was in Rome and discovered that you can still purchase absolution in some of the 100's of churches in Rome.  I thought that practice had ended centuries ago.

Honestly, I think that you must have either misunderstood what you saw being offered or it was done by some underhanded con artist who was trying to make money.  Actually, I don't think that one could ever "purchase absolution" within the Catholic faith even during the 16th century....I think the donation of money was linked more to the penance involved, not to absolution itself (unless it involved abuses done by individuals who were doing this on their own accord).  

It's called an indulgence and it was standard practice in the Middle Ages, especially after the Crusades for people to buy absolution for their sins. A good explanation of the practice is here, Reclaiming Our Roots p. 23 and here, IndulgencesIt is also one the practice that set Luther off and crystalized his objections to certain church practices. Here: Johann Tetzel  It was Luther specific objections to the practice of selling Indulgences that led him away from the Church.  I thought the practice had stopped.  As I said, I was shocked to find them selling Indulgences in the Churches of St John Lateran in Rome.  Incidentally, this church also holds a table that is traditionally held to to be the table at which Jesus sat during the last supper.