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 $85.57   10.581%   $94.6242   $94.62   $94.60   $94.60  
  Purchase #2 $35.39   7.110%   $37.9062   $37.91   $37.90   $37.90  
  Purchase #3 $235.28   13.747%   $267.6239   $267.62   $267.60   $267.60  
  Purchase #4 $55.43   8.754%   $60.2823   $60.28   $60.30   $60.30  
  Purchase #5 $235.61   8.554%   $255.7641   $255.76   $255.75   $255.80  
  Purchase #6 $42.76   10.684%   $47.3285   $47.33   $47.35   $47.30  
  Purchase #7 $172.27   5.805%   $182.2703   $182.27   $182.25   $182.30  
  7 purchase totals = $862.31       $945.7995   $945.79   $945.75   $945.80