Invoice Grouping Rule Attributes

Which optional grouping rule attribute consolidates detail ATO lines into top level invoice?  Example Order line 1.1 has sub lines 1.1.1, 1.1.2, 1.1.3... etc.  next line is 2.1  I am looking to group all the 1.1.x lines to invoice as 1.1

Order

1.1  Main item               1000.00

1.1.0  Feature                 100.00

1.1.2  Feature                 200.00

1.1.3  Feature                    0.00

1.1.4  Feature                   10.00

1.1.5  Feature                    0.00

2.1  Main Item (2)        2000.00

2.1.1  Feature (2)          500.00

I would like to group them where I have two lines / distributions based off of Main Item

Line 1  -  Main Item        1,310.00

Line 2  -  Main Item (2)   2,500.00

Thanks