Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $119.67   5.352%   $126.0747   $126.07   $126.05   $126.10  
  Purchase #2 $219.61   13.707%   $249.7119   $249.71   $249.70   $249.70  
  Purchase #3 $89.58   8.466%   $97.1638   $97.16   $97.15   $97.20  
  Purchase #4 $193.32   12.201%   $216.907   $216.91   $216.90   $216.90  
  Purchase #5 $55.63   8.795%   $60.5227   $60.52   $60.50   $60.50  
  Purchase #6 $111.84   5.840%   $118.3715   $118.37   $118.35   $118.40  
  Purchase #7 $221.65   7.821%   $238.9852   $238.99   $239.00   $239.00  
  7 purchase totals = $1,011.30       $1,107.7368   $1,107.73   $1,107.65   $1,107.80