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	$248.95	4.127%	$259.2242	$259.22	$259.20	$259.20
Purchase #2	$179.93	5.312%	$189.4879	$189.49	$189.50	$189.50
Purchase #3	$240.25	5.499%	$253.4613	$253.46	$253.45	$253.50
Purchase #4	$33.70	10.189%	$37.1337	$37.13	$37.15	$37.10
Purchase #5	$106.52	7.580%	$114.5942	$114.59	$114.60	$114.60
Purchase #6	$59.38	3.385%	$61.39	$61.39	$61.40	$61.40
Purchase #7	$144.42	6.751%	$154.1698	$154.17	$154.15	$154.20
7 purchase totals =	$1,013.15		$1,069.4611	$1,069.45	$1,069.45	$1,069.50