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 $233.85   4.344%   $244.0084   $244.01   $244.00   $244.00  
  Purchase #2 $146.88   11.685%   $164.0429   $164.04   $164.05   $164.00  
  Purchase #3 $235.99   10.730%   $261.3117   $261.31   $261.30   $261.30  
  Purchase #4 $195.93   5.722%   $207.1411   $207.14   $207.15   $207.10  
  Purchase #5 $63.90   5.642%   $67.5052   $67.51   $67.50   $67.50  
  Purchase #6 $97.32   4.675%   $101.8697   $101.87   $101.85   $101.90  
  Purchase #7 $102.39   4.324%   $106.8173   $106.82   $106.80   $106.80  
  7 purchase totals = $1,076.26       $1,152.6963   $1,152.70   $1,152.65   $1,152.60