Do check the corresponding MCSE though. If you are interested in the mean, mcse_mean will give you the expected deviation across MCMC fits using the same model on the same data. In your case for example, if it were 0.0005 and you want to report 3 significant digits you’ll need to get more MCMC samples (for example fitting again amd using az.concat to merge the two of them). We would like to take into account the mcse when rounding as default, but it is not the case yet.
Potentially useful reference: How many iterations to run and how many digits to report