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 $233.87   11.823%   $261.5205   $261.52   $261.50   $261.50  
  Purchase #2 $54.42   10.255%   $60.0008   $60.00   $60.00   $60.00  
  Purchase #3 $234.72   4.614%   $245.55   $245.55   $245.55   $245.60  
  Purchase #4 $28.99   5.851%   $30.6862   $30.69   $30.70   $30.70  
  Purchase #5 $177.94   3.765%   $184.6394   $184.64   $184.65   $184.60  
  Purchase #6 $178.78   6.625%   $190.6242   $190.62   $190.60   $190.60  
  Purchase #7 $130.78   7.513%   $140.6055   $140.61   $140.60   $140.60  
  7 purchase totals = $1,039.50       $1,113.6266   $1,113.63   $1,113.60   $1,113.60