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 $59.87   11.368%   $66.676   $66.68   $66.70   $66.70  
  Purchase #2 $218.45   8.786%   $237.643   $237.64   $237.65   $237.60  
  Purchase #3 $144.79   10.437%   $159.9017   $159.90   $159.90   $159.90  
  Purchase #4 $113.86   3.529%   $117.8781   $117.88   $117.90   $117.90  
  Purchase #5 $45.76   8.806%   $49.7896   $49.79   $49.80   $49.80  
  Purchase #6 $217.91   5.331%   $229.5268   $229.53   $229.55   $229.50  
  Purchase #7 $134.99   13.374%   $153.0436   $153.04   $153.05   $153.00  
  7 purchase totals = $935.63       $1,014.4588   $1,014.46   $1,014.55   $1,014.40