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 $163.69   11.476%   $182.4751   $182.48   $182.50   $182.50  
  Purchase #2 $196.95   10.567%   $217.7617   $217.76   $217.75   $217.80  
  Purchase #3 $193.47   11.713%   $216.1311   $216.13   $216.15   $216.10  
  Purchase #4 $43.67   8.160%   $47.2335   $47.23   $47.25   $47.20  
  Purchase #5 $159.71   6.127%   $169.4954   $169.50   $169.50   $169.50  
  Purchase #6 $133.97   11.715%   $149.6646   $149.66   $149.65   $149.70  
  Purchase #7 $195.89   8.291%   $212.1312   $212.13   $212.15   $212.10  
  7 purchase totals = $1,087.35       $1,194.8926   $1,194.89   $1,194.95   $1,194.90