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 $68.76   4.637%   $71.9484   $71.95   $71.95   $71.90  
  Purchase #2 $27.95   10.733%   $30.9499   $30.95   $30.95   $30.90  
  Purchase #3 $239.83   10.708%   $265.511   $265.51   $265.50   $265.50  
  Purchase #4 $238.75   4.571%   $249.6633   $249.66   $249.65   $249.70  
  Purchase #5 $205.63   8.682%   $223.4828   $223.48   $223.50   $223.50  
  Purchase #6 $120.34   4.295%   $125.5086   $125.51   $125.50   $125.50  
  Purchase #7 $238.71   4.581%   $249.6453   $249.65   $249.65   $249.60  
  7 purchase totals = $1,139.97       $1,216.7093   $1,216.71   $1,216.70   $1,216.60