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 $245.76   6.202%   $261.002   $261.00   $261.00   $261.00  
  Purchase #2 $176.56   7.646%   $190.0598   $190.06   $190.05   $190.10  
  Purchase #3 $184.48   4.181%   $192.1931   $192.19   $192.20   $192.20  
  Purchase #4 $169.81   8.198%   $183.731   $183.73   $183.75   $183.70  
  Purchase #5 $154.27   8.665%   $167.6375   $167.64   $167.65   $167.60  
  Purchase #6 $148.52   3.808%   $154.1756   $154.18   $154.20   $154.20  
  Purchase #7 $244.99   10.291%   $270.2019   $270.20   $270.20   $270.20  
  7 purchase totals = $1,324.39       $1,419.0009   $1,419.00   $1,419.05   $1,419.00