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 $114.38   9.852%   $125.6487   $125.65   $125.65   $125.60  
  Purchase #2 $89.30   4.305%   $93.1444   $93.14   $93.15   $93.10  
  Purchase #3 $209.93   13.185%   $237.6093   $237.61   $237.60   $237.60  
  Purchase #4 $43.31   6.514%   $46.1312   $46.13   $46.15   $46.10  
  Purchase #5 $187.92   9.676%   $206.1031   $206.10   $206.10   $206.10  
  Purchase #6 $69.58   7.305%   $74.6628   $74.66   $74.65   $74.70  
  Purchase #7 $94.76   5.221%   $99.7074   $99.71   $99.70   $99.70  
  7 purchase totals = $809.18       $883.0069   $883.00   $883.00   $882.90