This method you're using essentially plots the mark values against an axis for which you've used a constant field ([Field] in your example). The alignment of the marks is based on this value so none of the formatting alignment options will affect the fact that you're plotting values along an axis of '0'
If you show headers for the SUM(Field) measures in your columns shelf, those axes appear at the bottom for each column.
I'm sorry that this isn't a solution, just letting you know why you can't set the alignment as you would usually.
Thanks Steve, unfortunately I had to take this approach because I have a requirement to conditionally format some but not all of the measures in the table. We had gotten around this previously by building the dashboard out of many different worksheets, however I also have a requirement that the dashboard be viewed on tablets and the dashboard with so many worksheets would not scale/format properly at tablet resolution. I guess the layout became too complicated for tableau to know what to do with it.
Tableau seems to try to be helpful, when you perfectly align vertical or horizontal layout containers it automatically redoes the layout and replaces your containers with tiled layout containers. Which then broke my layout.
I was disappointed to see that Tableau 10 doesn't appear to contain any enhancements to it's ability to display tabular data. I understand tables of numbers are against tableau's religion but it is a necessary evil sometimes.
I've attached a screen shot of the original dashboard. You can see visually it's much nicer but it's made of 12 sheets as opposed to the new design which is made of only four (three with data and one that holds the headers), all of which span the whole page horizontally.
Tableau kills me sometimes.