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 $117.86   6.866%   $125.9523   $125.95   $125.95   $126.00  
  Purchase #2 $153.81   3.819%   $159.684   $159.68   $159.70   $159.70  
  Purchase #3 $52.66   4.408%   $54.9813   $54.98   $55.00   $55.00  
  Purchase #4 $8.60   4.335%   $8.9728   $8.97   $8.95   $9.00  
  Purchase #5 $209.42   12.171%   $234.9085   $234.91   $234.90   $234.90  
  Purchase #6 $73.92   9.396%   $80.8655   $80.87   $80.85   $80.90  
  Purchase #7 $193.42   6.555%   $206.0987   $206.10   $206.10   $206.10  
  7 purchase totals = $809.69       $871.4631   $871.46   $871.45   $871.60