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 $85.43   11.225%   $95.0195   $95.02   $95.00   $95.00  
  Purchase #2 $250.71   4.296%   $261.4805   $261.48   $261.50   $261.50  
  Purchase #3 $45.80   6.608%   $48.8265   $48.83   $48.85   $48.80  
  Purchase #4 $177.61   6.664%   $189.4459   $189.45   $189.45   $189.40  
  Purchase #5 $70.96   3.370%   $73.3514   $73.35   $73.35   $73.40  
  Purchase #6 $59.29   7.324%   $63.6324   $63.63   $63.65   $63.60  
  Purchase #7 $189.27   5.659%   $199.9808   $199.98   $200.00   $200.00  
  7 purchase totals = $879.07       $931.7370   $931.74   $931.80   $931.70