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 $202.40   5.748%   $214.034   $214.03   $214.05   $214.00  
  Purchase #2 $44.92   3.434%   $46.4626   $46.46   $46.45   $46.50  
  Purchase #3 $113.25   12.128%   $126.985   $126.99   $127.00   $127.00  
  Purchase #4 $13.25   11.385%   $14.7585   $14.76   $14.75   $14.80  
  Purchase #5 $32.47   7.369%   $34.8627   $34.86   $34.85   $34.90  
  Purchase #6 $65.41   3.776%   $67.8799   $67.88   $67.90   $67.90  
  Purchase #7 $60.86   13.694%   $69.1942   $69.19   $69.20   $69.20  
  7 purchase totals = $532.56       $574.1769   $574.17   $574.20   $574.30