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 $245.35   6.623%   $261.5995   $261.60   $261.60   $261.60  
  Purchase #2 $245.28   8.843%   $266.9701   $266.97   $266.95   $267.00  
  Purchase #3 $20.73   9.163%   $22.6295   $22.63   $22.65   $22.60  
  Purchase #4 $91.96   4.305%   $95.9189   $95.92   $95.90   $95.90  
  Purchase #5 $222.75   13.729%   $253.3313   $253.33   $253.35   $253.30  
  Purchase #6 $210.94   7.684%   $227.1486   $227.15   $227.15   $227.10  
  Purchase #7 $34.45   5.291%   $36.2727   $36.27   $36.25   $36.30  
  7 purchase totals = $1,071.46       $1,163.8706   $1,163.87   $1,163.85   $1,163.80