Well, if you're using the fixed weight version for now, keep at it--back cycling when you can't add weight will work for a while after that, if you're so inclined.
Doing what Rob suggests, 2 warmups and 3 'top' sets, will allow you to progress a bit more heavily just due to lower volume with your working weight.
Something you can do then (you can do it with the '5 working sets' version but it will be a bit more tedious) is to add weight to one set at a time. Thus: 2 warmups, a heavy set, and two backoffs. The next session, do your 2 warmups, two heavy sets, and one backoff. When you can hit the same weight for three sets, increase weight for the first again.
100x5 110x5 120x5x3 sets > 100x5 110x5 130x5 120x5x2 > 100x5 110x5 130x5x2 120x5 > 100x5 110x5 130x5x3 > 100x5 110x5 140x5 130x5x2 etc. etc.
Lots of ways to cook this, the 3-5x3-5 thing that is, simple and focused progression with heavy weights... works.