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	$217.48	5.583%	$229.6219	$229.62	$229.60	$229.60
Purchase #2	$173.42	13.146%	$196.2178	$196.22	$196.20	$196.20
Purchase #3	$127.80	12.157%	$143.3366	$143.34	$143.35	$143.30
Purchase #4	$217.56	13.836%	$247.6616	$247.66	$247.65	$247.70
Purchase #5	$198.72	13.486%	$225.5194	$225.52	$225.50	$225.50
Purchase #6	$205.74	7.183%	$220.5183	$220.52	$220.50	$220.50
Purchase #7	$46.88	13.111%	$53.0264	$53.03	$53.05	$53.00
7 purchase totals =	$1,187.60		$1,315.9020	$1,315.91	$1,315.85	$1,315.80