A possible brutal fix …
Fill your histogram using bins that produce nice results.
Afterwards, change the ranges of the axes of your histogram, like in the “Can we shift histogram for several channels?” thread: [url]Can we shift histogram for several channels?
You don’t even need to change the source code presented there (as TH3 and TH2 inherit from TH1, it should work fine - all the methods for “X”, “Y” and “Z” axes are there).