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 $147.89   10.798%   $163.8592   $163.86   $163.85   $163.90  
  Purchase #2 $186.36   7.133%   $199.6531   $199.65   $199.65   $199.70  
  Purchase #3 $23.63   5.778%   $24.9953   $25.00   $25.00   $25.00  
  Purchase #4 $98.60   9.194%   $107.6653   $107.67   $107.65   $107.70  
  Purchase #5 $233.71   7.863%   $252.0866   $252.09   $252.10   $252.10  
  Purchase #6 $69.88   12.481%   $78.6017   $78.60   $78.60   $78.60  
  Purchase #7 $222.60   5.590%   $235.0433   $235.04   $235.05   $235.00  
  7 purchase totals = $982.67       $1,061.9045   $1,061.91   $1,061.90   $1,062.00