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 $42.59   8.342%   $46.1429   $46.14   $46.15   $46.10  
  Purchase #2 $239.64   6.542%   $255.3172   $255.32   $255.30   $255.30  
  Purchase #3 $140.61   13.188%   $159.1536   $159.15   $159.15   $159.20  
  Purchase #4 $101.48   5.105%   $106.6606   $106.66   $106.65   $106.70  
  Purchase #5 $158.95   10.454%   $175.5666   $175.57   $175.55   $175.60  
  Purchase #6 $238.58   9.116%   $260.329   $260.33   $260.35   $260.30  
  Purchase #7 $241.41   8.418%   $261.7319   $261.73   $261.75   $261.70  
  7 purchase totals = $1,163.26       $1,264.9018   $1,264.90   $1,264.90   $1,264.90