How to earn the most munny on the "Junk" Job -
For 50 munny, you must clear all boxes within 10 hits or less. A good thing to note is that you can also shove the boxes together (albeit slowly), just by pushing into them. I have gotten them cleared quickly in just 7 hits, by starting with the box that is on the upper left (from when you're facing the field at the start). I hit this one straight across to the upper right, clearing out almost half the field. A triple-hit (combo) will destroy it, plus chain-reaction the ones near it. Then, I finish off the last couple boxes by hitting the one in the lower left across to the remining one or two on the lower right.