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 $61.61   11.444%   $68.6606   $68.66   $68.65   $68.70  
  Purchase #2 $210.63   12.165%   $236.2531   $236.25   $236.25   $236.30  
  Purchase #3 $56.84   12.757%   $64.0911   $64.09   $64.10   $64.10  
  Purchase #4 $132.83   9.459%   $145.3944   $145.39   $145.40   $145.40  
  Purchase #5 $44.35   9.299%   $48.4741   $48.47   $48.45   $48.50  
  Purchase #6 $97.89   7.254%   $104.9909   $104.99   $105.00   $105.00  
  Purchase #7 $51.52   10.778%   $57.0728   $57.07   $57.05   $57.10  
  7 purchase totals = $655.67       $724.9370   $724.92   $724.90   $725.10