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 $119.38   5.607%   $126.0736   $126.07   $126.05   $126.10  
  Purchase #2 $212.46   13.872%   $241.9325   $241.93   $241.95   $241.90  
  Purchase #3 $66.30   5.271%   $69.7947   $69.79   $69.80   $69.80  
  Purchase #4 $117.92   12.328%   $132.4572   $132.46   $132.45   $132.50  
  Purchase #5 $129.96   8.874%   $141.4927   $141.49   $141.50   $141.50  
  Purchase #6 $95.74   9.630%   $104.9598   $104.96   $104.95   $105.00  
  Purchase #7 $85.86   10.311%   $94.713   $94.71   $94.70   $94.70  
  7 purchase totals = $827.62       $911.4235   $911.41   $911.40   $911.50