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 $76.63   12.801%   $86.4394   $86.44   $86.45   $86.40  
  Purchase #2 $195.82   10.485%   $216.3517   $216.35   $216.35   $216.40  
  Purchase #3 $13.89   4.823%   $14.5599   $14.56   $14.55   $14.60  
  Purchase #4 $72.74   3.690%   $75.4241   $75.42   $75.40   $75.40  
  Purchase #5 $21.49   4.196%   $22.3917   $22.39   $22.40   $22.40  
  Purchase #6 $176.98   5.764%   $187.1811   $187.18   $187.20   $187.20  
  Purchase #7 $146.50   3.701%   $151.922   $151.92   $151.90   $151.90  
  7 purchase totals = $704.05       $754.2699   $754.26   $754.25   $754.30