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 $63.63   9.269%   $69.5279   $69.53   $69.55   $69.50  
  Purchase #2 $122.49   10.149%   $134.9215   $134.92   $134.90   $134.90  
  Purchase #3 $210.62   12.468%   $236.8801   $236.88   $236.90   $236.90  
  Purchase #4 $25.89   4.241%   $26.988   $26.99   $27.00   $27.00  
  Purchase #5 $196.81   5.139%   $206.9241   $206.92   $206.90   $206.90  
  Purchase #6 $213.88   7.755%   $230.4664   $230.47   $230.45   $230.50  
  Purchase #7 $210.60   11.213%   $234.2146   $234.21   $234.20   $234.20  
  7 purchase totals = $1,043.92       $1,139.9226   $1,139.92   $1,139.90   $1,139.90