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 $11.41   11.635%   $12.7376   $12.74   $12.75   $12.70  
  Purchase #2 $19.89   13.784%   $22.6316   $22.63   $22.65   $22.60  
  Purchase #3 $166.26   3.386%   $171.8896   $171.89   $171.90   $171.90  
  Purchase #4 $185.89   12.251%   $208.6634   $208.66   $208.65   $208.70  
  Purchase #5 $237.66   10.302%   $262.1437   $262.14   $262.15   $262.10  
  Purchase #6 $63.71   5.224%   $67.0382   $67.04   $67.05   $67.00  
  Purchase #7 $186.83   10.798%   $207.0039   $207.00   $207.00   $207.00  
  7 purchase totals = $871.65       $952.1080   $952.10   $952.15   $952.00