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 $68.44   10.470%   $75.6057   $75.61   $75.60   $75.60  
  Purchase #2 $106.80   9.199%   $116.6245   $116.62   $116.60   $116.60  
  Purchase #3 $78.50   9.438%   $85.9088   $85.91   $85.90   $85.90  
  Purchase #4 $196.70   3.136%   $202.8685   $202.87   $202.85   $202.90  
  Purchase #5 $25.91   5.711%   $27.3897   $27.39   $27.40   $27.40  
  Purchase #6 $146.76   7.545%   $157.833   $157.83   $157.85   $157.80  
  Purchase #7 $35.66   7.829%   $38.4518   $38.45   $38.45   $38.50  
  7 purchase totals = $658.77       $704.6820   $704.68   $704.65   $704.70