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 $201.75   3.223%   $208.2524   $208.25   $208.25   $208.30  
  Purchase #2 $197.69   12.664%   $222.7255   $222.73   $222.75   $222.70  
  Purchase #3 $162.55   12.539%   $182.9321   $182.93   $182.95   $182.90  
  Purchase #4 $242.84   9.594%   $266.1381   $266.14   $266.15   $266.10  
  Purchase #5 $249.75   10.670%   $276.3983   $276.40   $276.40   $276.40  
  Purchase #6 $249.43   6.623%   $265.9497   $265.95   $265.95   $265.90  
  Purchase #7 $184.40   10.430%   $203.6329   $203.63   $203.65   $203.60  
  7 purchase totals = $1,488.41       $1,626.0290   $1,626.03   $1,626.10   $1,625.90