Account Invoice Tax - Computation By Column

    
    -Invoice taxes: 
        legend:
            TA(l)    TaxAmount for line l
            TBA(l)   TaxBaseAmount for line l
            TA(t)    TaxAmount for tax t
            TBA(t)   TaxBaseAmount for tax t
            
        default behaviour: 
            openerp by default calculates taxes line by line as a function of line tax base amount 
            and then groups these amounts by tax.
            TA(l) = f(TBA(l)
            TA(t) = sum( round( TA(l) ) )    /sum on lines l to which tax t is applied
        this module behaviour: 
            In Italy the correct way to compute taxes is to first compute the tax base amount TBA(t) 
            and the compute TA as a function of TBA(t)
            TBA(t) = sum( TBA(t) )    /sum on lines l to which tax t is applied
            TA(t) = f( TBA(t) )
        the result difference is small but important

    NOTE
    ====
    
    For OpenERP 6.1, please use the patch contained in the following branch:
https://code.launchpad.net/~openerp-community/openobject-addons/fix-account-6-1-tax-computation-method
instead of this module

    For OpenERP > 6.1, the fix has been merged yet:
https://code.launchpad.net/~akretion-team/openobject-addons/trunk-add-tax-rounding-option/+merge/113833
so this module is not needed anymore