I remember that I heard something like this, that for a certain sample size one should not give more than $n$ decimal places for location and dispersion parameters e.g. for small samples sizes only one decimal place, for larger ones two or even more.
But I can absolutely find no information on this topic. There is this article: http://adc.bmj.com/content/early/2015/04/15/archdischild-2014-307149.full which has some rules as a table but there is no hints about the sample size.
One interesting thing here is also that the paper states for test statistic, only one decimal place and max. 2 significant places should be given. In a statistics course we were taught to give test statistic results to at least 6 decimal places.