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 $106.93   5.260%   $112.5545   $112.55   $112.55   $112.60  
  Purchase #2 $244.76   6.755%   $261.2935   $261.29   $261.30   $261.30  
  Purchase #3 $231.39   5.630%   $244.4173   $244.42   $244.40   $244.40  
  Purchase #4 $147.91   13.697%   $168.1692   $168.17   $168.15   $168.20  
  Purchase #5 $26.40   3.305%   $27.2725   $27.27   $27.25   $27.30  
  Purchase #6 $29.65   8.382%   $32.1353   $32.14   $32.15   $32.10  
  Purchase #7 $34.86   5.490%   $36.7738   $36.77   $36.75   $36.80  
  7 purchase totals = $821.90       $882.6161   $882.61   $882.55   $882.70