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 $149.50   8.758%   $162.5932   $162.59   $162.60   $162.60  
  Purchase #2 $157.79   10.518%   $174.3864   $174.39   $174.40   $174.40  
  Purchase #3 $67.34   13.168%   $76.2073   $76.21   $76.20   $76.20  
  Purchase #4 $68.93   6.240%   $73.2312   $73.23   $73.25   $73.20  
  Purchase #5 $244.58   6.782%   $261.1674   $261.17   $261.15   $261.20  
  Purchase #6 $224.99   9.779%   $246.9918   $246.99   $247.00   $247.00  
  Purchase #7 $41.95   12.555%   $47.2168   $47.22   $47.20   $47.20  
  7 purchase totals = $955.08       $1,041.7941   $1,041.80   $1,041.80   $1,041.80