T-SQL (SS2K8) :: Moving Values To Fill In Nulls?

I have been away from SQL for a couple of months, and for the life of me cannot work out a simple way to do what i want to do.

select bu1.name,bu2.name, bu3.name, bu4.name, bu5.name
from
Sale
INNER JOIN
Sysuser on sale.userid = sysuser.userid
INNER JOIN businessunitBU1
on BU1.Businessunitid = sysuser.businessunitid
left JOIN businessunitBU2
on BU2.Businessunitid = bu1.parentbusinessunitid
left JOIN businessunitBU3
on BU3.Businessunitid = bu2.parentbusinessunitid
left JOIN businessunitBU4
on BU4.Businessunitid = bu3.parentbusinessunitid
left JOIN businessunitBU5
on BU5.Businessunitid = bu4.parentbusinessunitid

So effectively i am trying to go through the hierarchy to find all the levels. Unforunately not every entry has the same amount of levels.

So its coming out like this.....

Bu1 BU2 BU3 BU4 BU5
L5 L4 L3 L2 L1
L4 L3 L2 L1
L3 L2 L1
L5 L4 L3 L2 L1

So whats the easiest way to move everything along to fill in the blanks, but move the blanks to the end - so it would be more like this:

Bu1 BU2 BU3 BU4 BU5
L5 L4 L3 L2 L1
L4 L3 L2 L1
L3 L2 L1
L5 L4 L3 L2 L1