What does a grocery store do with food that’s got to go and isn’t selling? I like the idea of dismantling the megacorp strategy, but I can’t help thinking it would lead to a lot of unnecessary waste as companies just throw things out instead of trying to recoup a small fraction of their investment.

That's an ill-thought out law. Bigger companies can run at cost or reduced profit and still out compete smaller companies due to economies of scale and diversified income streams.

I'm fairly certain that that only applies to standard pricing, not discounts and promotions that run for a limited time.