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	$100.74	4.859%	$105.635	$105.64	$105.65	$105.60
Purchase #2	$100.49	13.504%	$114.0602	$114.06	$114.05	$114.10
Purchase #3	$199.40	5.142%	$209.6531	$209.65	$209.65	$209.70
Purchase #4	$182.68	4.256%	$190.4549	$190.45	$190.45	$190.50
Purchase #5	$52.87	6.422%	$56.2653	$56.27	$56.25	$56.30
Purchase #6	$203.49	13.277%	$230.5074	$230.51	$230.50	$230.50
Purchase #7	$163.62	3.363%	$169.1225	$169.12	$169.10	$169.10
7 purchase totals =	$1,003.29		$1,075.6984	$1,075.70	$1,075.65	$1,075.80