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 $68.41   8.411%   $74.164   $74.16   $74.15   $74.20  
  Purchase #2 $160.56   4.722%   $168.1416   $168.14   $168.15   $168.10  
  Purchase #3 $227.76   11.299%   $253.4946   $253.49   $253.50   $253.50  
  Purchase #4 $54.64   3.866%   $56.7524   $56.75   $56.75   $56.80  
  Purchase #5 $180.78   11.397%   $201.3835   $201.38   $201.40   $201.40  
  Purchase #6 $189.46   3.821%   $196.6993   $196.70   $196.70   $196.70  
  Purchase #7 $215.33   5.526%   $227.2291   $227.23   $227.25   $227.20  
  7 purchase totals = $1,096.94       $1,177.8645   $1,177.85   $1,177.90   $1,177.90