Thanks Shane, I think I've narrowed down where the inconsistency is coming from - I can get the bottom axis to format as currency and sort properly when I'm pulling directly from a table using a simple query as described (also note I'm trying to graph two currency values both as primary values). However, when using a Union query (in my case pulling from 3 tables, and yes the data appears correctly when viewing it), the graph will not render the second value at all, and also the bottom axis does not sort properly until I add the first value. If I replicate that same dataset to a temporary table, then use a simple query against it, it appears to work fine with both values rendered on the graph properly as currency. So near as I can figure the graph doesn't appear to like Union queries.
Didn't mean for this to turn into a trouble ticket, but I do appreciate the input. BTW, my version of Office shows as "Microsoft Office 365 Pro Plus", version 1902 build 11328.20318 click-to-run.