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 $148.61   3.626%   $153.9986   $154.00   $154.00   $154.00  
  Purchase #2 $44.32   5.567%   $46.7873   $46.79   $46.80   $46.80  
  Purchase #3 $187.87   3.835%   $195.0748   $195.07   $195.05   $195.10  
  Purchase #4 $48.29   13.568%   $54.842   $54.84   $54.85   $54.80  
  Purchase #5 $89.49   3.578%   $92.692   $92.69   $92.70   $92.70  
  Purchase #6 $242.89   7.716%   $261.6314   $261.63   $261.65   $261.60  
  Purchase #7 $60.80   6.564%   $64.7909   $64.79   $64.80   $64.80  
  7 purchase totals = $822.27       $869.8170   $869.81   $869.85   $869.80