cart can have a negative total if there's a promotion larger than the cart cost

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What steps will reproduce the problem?
1. create large promotion [like 100 dollars] 
2.  choose one cheap item, enter that promotion on checkout
3.

What is the expected output? What do you see instead?
shoudl have $0 for the total cart price.

There's also an edge case where what if there's no shipping cost and the 
total is really zero on checkout--should it then just skip the 
authorize.net charge totally? [or does zero actually clear all right?] But 
that's another issue for another day.
-=R

Original issue reported on code.google.com by rogerpack2005 on 8 Dec 2008 at 9:42

[GoogleCodeExporter]

Original comment by subim...@gmail.com on 4 May 2010 at 7:18

• Added labels: Priority-High
• Removed labels: Priority-Medium

[GoogleCodeExporter]

Fixed, r227

Original comment by subim...@gmail.com on 5 May 2010 at 7:36

• Changed state: Fixed