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	$67.72	5.852%	$71.683	$71.68	$71.70	$71.70
Purchase #2	$128.61	11.462%	$143.3513	$143.35	$143.35	$143.40
Purchase #3	$131.56	10.187%	$144.962	$144.96	$144.95	$145.00
Purchase #4	$113.45	8.264%	$122.8255	$122.83	$122.85	$122.80
Purchase #5	$39.77	3.348%	$41.1015	$41.10	$41.10	$41.10
Purchase #6	$177.32	13.167%	$200.6677	$200.67	$200.65	$200.70
Purchase #7	$11.80	12.465%	$13.2709	$13.27	$13.25	$13.30
7 purchase totals =	$670.23		$737.8619	$737.86	$737.85	$738.00