firstly you should decide on which database event (if you are requiring database trigger) should this trigger fire. Or, is it somehow connected with the application whichever language it is written in? Then you would post more about it, would not you?
I see a vague requirement and a table description. Unfortunately, there is no map between them in your post. Based on this I would say: I would not write any trigger, just INSERT statement based on "sale" properties entered somehow somewhere on the time (or shortly after) "sale was made".