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 $244.42   6.856%   $261.1774   $261.18   $261.20   $261.20  
  Purchase #2 $246.69   12.570%   $277.6989   $277.70   $277.70   $277.70  
  Purchase #3 $162.39   8.249%   $175.7856   $175.79   $175.80   $175.80  
  Purchase #4 $21.55   3.182%   $22.2357   $22.24   $22.25   $22.20  
  Purchase #5 $187.90   3.871%   $195.1736   $195.17   $195.15   $195.20  
  Purchase #6 $10.43   4.156%   $10.8635   $10.86   $10.85   $10.90  
  Purchase #7 $76.62   6.519%   $81.6149   $81.61   $81.60   $81.60  
  7 purchase totals = $950.00       $1,024.5496   $1,024.55   $1,024.55   $1,024.60