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 $59.67   6.789%   $63.721   $63.72   $63.70   $63.70  
  Purchase #2 $59.95   9.206%   $65.469   $65.47   $65.45   $65.50  
  Purchase #3 $54.53   6.438%   $58.0406   $58.04   $58.05   $58.00  
  Purchase #4 $234.60   5.670%   $247.9018   $247.90   $247.90   $247.90  
  Purchase #5 $122.49   6.697%   $130.6932   $130.69   $130.70   $130.70  
  Purchase #6 $196.84   6.316%   $209.2724   $209.27   $209.25   $209.30  
  Purchase #7 $5.66   10.457%   $6.2519   $6.25   $6.25   $6.30  
  7 purchase totals = $733.74       $781.3499   $781.34   $781.30   $781.40