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 $119.71   4.656%   $125.2837   $125.28   $125.30   $125.30  
  Purchase #2 $217.63   9.414%   $238.1177   $238.12   $238.10   $238.10  
  Purchase #3 $196.76   6.110%   $208.782   $208.78   $208.80   $208.80  
  Purchase #4 $138.71   12.723%   $156.3581   $156.36   $156.35   $156.40  
  Purchase #5 $16.60   8.458%   $18.004   $18.00   $18.00   $18.00  
  Purchase #6 $176.99   10.730%   $195.981   $195.98   $196.00   $196.00  
  Purchase #7 $237.68   9.859%   $261.1129   $261.11   $261.10   $261.10  
  7 purchase totals = $1,104.08       $1,203.6394   $1,203.63   $1,203.65   $1,203.70