Typically, when the price is highly visible to the consumer, certain price points work best: 0.99, 1.49, etc. You don't price an app or a hamburger at 1.82. To achieve that, you "bundle" your price increases.
A similar aesthetic could be achieved by showing the attractive USD price, and the converted price in a smaller font, or even on a different page/view/whatever (although that's kind of shitty). I've seen this approach in a few places.
Not having done forex, my guess is that *most* of the time, the major currencies would drift within a few percentage points of each other week to week, so sticking with 0.99 would work better than 1.02 one day, 1.01 the next, then 0.98. 1 is psychological cut-off, going above that reduces sales.
If it was that simple, I'd be a Forex millionaire by now, as would many others, since buying each dip would be a viable strategy. Unfortunately (or fortunately, since I didn't go broke), I ultimately threw out about 6 months of development into a complex algorithmic trading system that targeted Forex. Bear in mind I did that as somebody that's not afraid to take risks; unfortunately, currency pairs swing wildly, even when no geopolitical events can be easily attributed to the fluctuations.
To get an idea, take a look at the 52-week pictures for a few currency pairs:
These are major currency pairs, and as you can see, they move wildly on a daily basis, let alone weekly or monthly. Sometimes there are obvious events such as Brexit, but most of the time it's due to innumerable factors and a dash of irrationality. Fixed currency conversion rates do not have a place in modern society, and are almost always a scam. What Apple is doing is wrong, and I'm sure at least some of the people involved know.
Nothing ever becomes real till it is experienced -- even a proverb is no proverb to you till your life has illustrated it. -- John Keats