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	$38.98	4.558%	$40.7567	$40.76	$40.75	$40.80
Purchase #2	$50.39	7.274%	$54.0554	$54.06	$54.05	$54.10
Purchase #3	$243.85	11.599%	$272.1342	$272.13	$272.15	$272.10
Purchase #4	$159.62	8.425%	$173.068	$173.07	$173.05	$173.10
Purchase #5	$208.50	7.163%	$223.4349	$223.43	$223.45	$223.40
Purchase #6	$230.45	8.160%	$249.2547	$249.25	$249.25	$249.30
Purchase #7	$113.64	5.143%	$119.4845	$119.48	$119.50	$119.50
7 purchase totals =	$1,045.43		$1,132.1884	$1,132.18	$1,132.20	$1,132.30