So, in the context of the template Hanley suggested:
Mon: Bench x5, drop 5-10% for 2 more sets; Press: 10 min amrap
Tues: Squat x5, drop 5-10% for 2 more sets; Light pull (maybe RDLs for 3x8?)
wed. off
Thurs: repeat mon. with added load on bench; and try for 1-2 extra reps during press amrap
Fri: Squat: same as Tues. Add load. Dead: 5, then 10% drop for 1-2 more sets of 5
As written, there are five opportunities for new 5RMs each week. Don't worry - you probably wouldn't be able to sustain progress like that - constantly working at the maximum output is very taxing. When doing the drop sets - more opportunities to set PRs. Maybe instead of doing sets of 5, maybe crank out a really hard set of 8 with the same weight. Personally, I'm pretty lazy, and I've made a deal with myself. If I can set a new PR - I can be done with a lift. So, instead of doing two backoff sets, I would do one all-out, can't do-another-rep set. And so I earn a new PR.
Regarding 10s and 20s, specificity plays a big part (i.e., practicing higher reps makes you better at doing higher reps), but you could also toss them in every once in a while. Use them sparingly - they definitely take a lot to recover from. In general though, a 10RM is ~70% of 1RM, and a 20RM is ~60% 1RM. Using your 5x5 weight of 320, that probably means you have a 1RM around 415. Let's say you set a new 5RM of 355 some day, and you feel great. So great that you want to keep squatting and skip deadlifts. If you were to load 225-250 onto the bar, it would feel incredibly light (like a backpack). At that point, you could crank out a set of 20, where the last 10 reps make you question your sanity. Or get a new 10RM with 290-300.