You may not even need to round using a beast mode calculation. It seems like you are using a textbox chart, however for have you tried using the single value chart? It is a similar chart, and if you look in Chart Properties>General>Decimal Places, you will be able to select how many decimal places you would like to show.
Hi Mark, Thanks for the response, it was not letting me reply before. To give you an idea, each box of the treemap represents a different machine. The goal would be to organize the boxes in a manner so that it replicates the layout of our machine shop.