If you find things are not working per what is documented in the Help, there are only two things I could suggest, check that you are running the latest service release (SR) for the major version you are running, these are:
If you are on one of those, then this may be something defect related, and will likely be best to open a support case with us at that point, if you can provide an example app if you do that, that should help us check things pretty quickly.
To help users find verified answers, please do not forget to use the "Accept as Solution" button on any post(s) that helped you resolve your problem or question. I now work a compressed schedule, Tuesday, Wednesday and Thursday, so those will be the days I will reply to any follow-up posts.
@marcus_sommer : Your solution give me the result expected. I wonder if there is a way to optimize the second parameter of the function round(), for example to precise directly the number of decimals. Maybe not with the function round(), but if there is another function in QVW I will be really interesting to know it ?!