SQL & PL/SQL :: Sum Daily Total To Weekly In Oracle?

I need to sum the below daily total to weekly with the week starting day of Saturday Jan 3 2009 for the 52 weeks in 2009. The below query provides me the weekly total with the week starting day MONDAY. But I need the week starting day to be SATURDAY instead of MONDAY.

select to_char(report_date, 'YYYYIW'), sum(total)
from report_table
where to_number(to_char(report_date,'YYYYIW')) >=
to_number(to_char(to_date( '&one_year_ago'),'YYYYIW'))
group by to_char(report_date, 'YYYYIW')

Here is a query I used to generate the Daily Sample Data:

SELECT DISTINCT A.PRODUCT, TO_CHAR(B.BEGIN_DT,'YYYY-MM-DD') as post_date,'RCSL', A.DEPTID, A.ACCOUNT, SUM( A.POSTED_TOTAL_AMT) as Amount_Posted
FROM A, B, C
AND B.BEGIN_DT BETWEEN TO_DATE('&StartDate','YYYY-MM-DD') AND TO_DATE('&EndDate','YYYY-MM-DD')
GROUP BY A.PRODUCT, TO_CHAR(B.BEGIN_DT,'YYYY-MM-DD'), A.DEPTID, A.ACCOUNT

For the below sample data I would need to add data starting 2010-01-02 - 2010-01-08 to get my weekly total.

7777,2010-01-01,RCSL,0170,331062,-85
7777,2010-01-02,RCSL,0170,331063,-190
7777,2010-01-03,RCSL,0170,341413,170.18
7777,2010-01-04,RCSL,0170,347103,-880
7777,2010-01-05,RCSL,0172,331050,-116
7777,2010-01-06,RCSL,0172,331053,-50
7777,2010-01-07,RCSL,0172,331061,-63
7777,2010-01-08,RCSL,0172,331061,-63