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 $44.88   4.366%   $46.8395   $46.84   $46.85   $46.80  
  Purchase #2 $9.31   5.497%   $9.8218   $9.82   $9.80   $9.80  
  Purchase #3 $104.69   10.795%   $115.9913   $115.99   $116.00   $116.00  
  Purchase #4 $201.90   4.188%   $210.3556   $210.36   $210.35   $210.40  
  Purchase #5 $93.51   3.721%   $96.9895   $96.99   $97.00   $97.00  
  Purchase #6 $14.81   13.152%   $16.7578   $16.76   $16.75   $16.80  
  Purchase #7 $244.75   6.698%   $261.1434   $261.14   $261.15   $261.10  
  7 purchase totals = $713.85       $757.8989   $757.90   $757.90   $757.90