Funny you posted this. I was noticing the same thing. My data source is a base sas table (no information map, just proc sql code) - I tried changing the formats within the sas table itself and then within the proc sql code. It actually was resetting EVERYTHING to BEST. format. So I even loose my $ signs.
Anyhow, you can run the following statement during your SAS ETL to round to the nearest .1 decimal place:
val=round(val, .1)
(you could change .1 to 0.01 to round to nearest one-hundredth ~ for instance)
I am pretty sure you could customize the expression in your information map to also do this. I'll test that idea next.
~ Angela Hall
http://sas-bi.blogspot.com