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 $115.93   9.183%   $126.5759   $126.58   $126.60   $126.60  
  Purchase #2 $205.63   8.413%   $222.9297   $222.93   $222.95   $222.90  
  Purchase #3 $30.86   10.233%   $34.0179   $34.02   $34.00   $34.00  
  Purchase #4 $99.44   6.181%   $105.5864   $105.59   $105.60   $105.60  
  Purchase #5 $53.58   8.566%   $58.1697   $58.17   $58.15   $58.20  
  Purchase #6 $152.66   12.493%   $171.7318   $171.73   $171.75   $171.70  
  Purchase #7 $32.65   7.118%   $34.974   $34.97   $34.95   $35.00  
  7 purchase totals = $690.75       $753.9854   $753.99   $754.00   $754.00