to be fair, having only 2 decimal places isn't an inherent feature of government currencies; it's simply the way banks and other institutions store amounts.
there's no reason why a pack of gum couldn't cost $0.4529839 if being paid for electronically.
In theory, yes. In practice, we are heavily dependent on tons and TONS of bank & payment infrastructures, with billions of different standards and implementations.
It's indeed the way the banks work, as you already mention, and there's no simple way around them if you want to stick with euros and dollars.
It would be virtually IMPOSSIBLE to get $ 0.000001 units actually working in practice, and would at least take many many many years of development, insane debugging / hacking / workarounds, deciphering tons of spaghetti code on crummy old systems, and disentangling a plethora of highly non-standardized finance processing programs, modules and servers. Not gonna happen.
Bitcoin, on the other hand, is very clear about this in its protocol specifications (theory) AND it's been implemented perfectly in every client (practice). So, there's one problem that Bitcoin solves.