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 $105.61   8.195%   $114.2647   $114.26   $114.25   $114.30  
  Purchase #2 $179.39   12.401%   $201.6362   $201.64   $201.65   $201.60  
  Purchase #3 $99.48   5.673%   $105.1235   $105.12   $105.10   $105.10  
  Purchase #4 $117.69   4.661%   $123.1755   $123.18   $123.20   $123.20  
  Purchase #5 $8.97   10.611%   $9.9218   $9.92   $9.90   $9.90  
  Purchase #6 $17.59   13.376%   $19.9428   $19.94   $19.95   $19.90  
  Purchase #7 $143.73   11.274%   $159.9341   $159.93   $159.95   $159.90  
  7 purchase totals = $672.46       $733.9986   $733.99   $734.00   $733.90