I don't see anywhere in the rules as to whether you round up or down if the situation arises. Is there a blanket rule for this or is it a case by case basis depending on the situation?

That's a traditional weakness of Shadowrun, and it's traditionally left as an exercise for the reader to extrapolate from other rulings in similar situations.

Other than that, it's pretty much house rule territory... and mostly, it's best to consider the result, even if it is explicitly mentioned:

The SR4 rules explicitly allowed for an amount of hardpoints equal to a third of body, rounded up. Which meant that you could install a sniper rifle on a Minidrone with Body 1, and a tank railgun on a Heavy Drone with Body 4.
SR4A changed that to a third of body, rounded down.

Thanks!

One of the good aspects of SR5 was that it established a default rule for that...which SR6 immediately discarded again.

A NOTE ON ROUNDING
Sometimes you’re going to have to divide some number or another, and sometimes that will require rounding. The general rule of thumb is to round up, unless a specific rule tells you to do otherwise.

And SR3 seems mostly to be a rounding down system - drain for spells, karma cost, working out reaction and combat pool.
On the whole it's probably best to do a bit of testing on your rules system, have a look at some edge cases or abusable situations, and then go with at least a house rule or interpretation of "what was intended" to use at your table consistently.