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 $201.50   3.245%   $208.0387   $208.04   $208.05   $208.00  
  Purchase #2 $57.38   6.179%   $60.9255   $60.93   $60.95   $60.90  
  Purchase #3 $180.51   7.808%   $194.6042   $194.60   $194.60   $194.60  
  Purchase #4 $234.99   5.180%   $247.1625   $247.16   $247.15   $247.20  
  Purchase #5 $161.27   4.628%   $168.7336   $168.73   $168.75   $168.70  
  Purchase #6 $237.70   6.602%   $253.393   $253.39   $253.40   $253.40  
  Purchase #7 $121.69   8.689%   $132.2636   $132.26   $132.25   $132.30  
  7 purchase totals = $1,195.04       $1,265.1211   $1,265.11   $1,265.15   $1,265.10