The trouble is, i need the rounding to occur prior to being displayed on the BOM. I would prefer it if my colleagues did not have to implement equations on line items that are being evaluated as decimals.
I did visit that page yesterday and used it to successfully round my global variable.. only to realize that I just ensured it would double the quantity and not just add 10% 
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Whenever I see people doing gymnastics with their BOMs, I wonder if they have ever considered handling the problem at the source: the assembly. This problem seems like a good candidate for a macro, or better yet a macro feature. If these items represent spares and such, why not add the actual items as parts in the assembly? They could go in a ‘Spares’ folder, whose components are all hidden but would appropriately increase the BOM quantities.
Now, how to automate this? Macro feature to the rescue. On every rebuild, the macro feature can traverse the assembly components, checking them for a particular custom property, doing the appropriate calculation (with the full math capabilities of an actual programming language at your disposal) and then add the required number of extra copies of that part to the ‘Spares’ folder.
You could even implement this as a macro feature per component where the user can indicate the desired ‘percentage extra’ for a selected component. Then the part files wouldn’t need any sort of property at all. It would happen at the component level in the assembly. This would allow different percentages for different jobs/customers as long as the assembly was unique to that customer.
I’d work on this but I’m too busy with my real job… 
As with most problems users face with this software, there is typically more than 1 way to find a solution. Some require more experience than others and unfortunately, macro creation and editing is not a skill i possess. I don’t disagree with your assessment however, that an alternative solution to this problem could be to look more closely as ways of including the spare components as actual parts ; its just if can I create a way to do that, that is clear and obvious to the person building the project. We manage hardware a little differently than most I’m sure, but in a way that works really well for the equipment we build.
For consistencies sake, if I can manage to find way of doing it through the property tab builder and custom properties, it would be my preference. Its a bit of “tunnel vision” on my part perhaps. I’ll update if i find a solution.
All the help and feedback I’ve received so far has helped me crack more than a few nuts, so I appreciate all of it I can get. 
Instead of a question, here’s something I’ve figured out that was a nice breakthrough for what I’m trying to accomplish.
Because I am creating a text string using properties from the model, I was trying to dertermine how I could also toggle those outputs for different scenarios. For instance, sometimes our projects are built using the Inside Diameter as the governing surface, sometime they use the Outside Diameter. A dimension will only allow you one result.
What i discovered, is you can nest a property within another property. For example, if the dimension name is “Cylinder OD@Sketch1” you can create a custom property selection in your poperty tab builder that evaluates a property name (EX: $PRP:”Profile_Match”)
Now, in your text string, replace the “OD” with the property name:
Cylinder $PRP:”Profile_Match”@Sketch1Sketch1
As long as you have a dimension named Cylinder OD and a dimension named Cylinder ID, that property will toggle which dimension is being evaluated, and will update the result in your property string.
Ive gone on to use this on numerous components to allow our users to make selections from different options, based on what the job might entail. All without having to do any manual manipulation of the property string already created for them.
