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 $98.61   6.475%   $104.995   $105.00   $105.00   $105.00  
  Purchase #2 $114.73   5.547%   $121.0941   $121.09   $121.10   $121.10  
  Purchase #3 $16.39   4.685%   $17.1579   $17.16   $17.15   $17.20  
  Purchase #4 $200.81   10.506%   $221.9071   $221.91   $221.90   $221.90  
  Purchase #5 $124.98   8.523%   $135.632   $135.63   $135.65   $135.60  
  Purchase #6 $164.63   5.674%   $173.9711   $173.97   $173.95   $174.00  
  Purchase #7 $165.73   5.412%   $174.6993   $174.70   $174.70   $174.70  
  7 purchase totals = $885.88       $949.4565   $949.46   $949.45   $949.50