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 $102.45   11.274%   $114.0002   $114.00   $114.00   $114.00  
  Purchase #2 $152.90   8.411%   $165.7604   $165.76   $165.75   $165.80  
  Purchase #3 $91.95   11.686%   $102.6953   $102.70   $102.70   $102.70  
  Purchase #4 $196.66   5.112%   $206.7133   $206.71   $206.70   $206.70  
  Purchase #5 $49.53   12.318%   $55.6311   $55.63   $55.65   $55.60  
  Purchase #6 $230.74   10.271%   $254.4393   $254.44   $254.45   $254.40  
  Purchase #7 $48.53   3.808%   $50.378   $50.38   $50.40   $50.40  
  7 purchase totals = $872.76       $949.6176   $949.62   $949.65   $949.60