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	$215.41	3.484%	$222.9149	$222.91	$222.90	$222.90
Purchase #2	$207.91	7.165%	$222.8068	$222.81	$222.80	$222.80
Purchase #3	$131.65	9.212%	$143.7776	$143.78	$143.80	$143.80
Purchase #4	$156.60	7.619%	$168.5314	$168.53	$168.55	$168.50
Purchase #5	$24.85	6.354%	$26.429	$26.43	$26.45	$26.40
Purchase #6	$213.42	4.711%	$223.4742	$223.47	$223.45	$223.50
Purchase #7	$87.58	12.869%	$98.8507	$98.85	$98.85	$98.90
7 purchase totals =	$1,037.42		$1,106.7846	$1,106.78	$1,106.80	$1,106.80