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 $69.28   10.692%   $76.6874   $76.69   $76.70   $76.70  
  Purchase #2 $114.59   7.155%   $122.7889   $122.79   $122.80   $122.80  
  Purchase #3 $122.83   8.321%   $133.0507   $133.05   $133.05   $133.10  
  Purchase #4 $97.25   9.786%   $106.7669   $106.77   $106.75   $106.80  
  Purchase #5 $146.63   5.293%   $154.3911   $154.39   $154.40   $154.40  
  Purchase #6 $221.97   4.808%   $232.6423   $232.64   $232.65   $232.60  
  Purchase #7 $5.99   11.365%   $6.6708   $6.67   $6.65   $6.70  
  7 purchase totals = $778.54       $832.9981   $833.00   $833.00   $833.10