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	$247.75	5.152%	$260.5141	$260.51	$260.50	$260.50
Purchase #2	$33.54	10.492%	$37.059	$37.06	$37.05	$37.10
Purchase #3	$65.74	7.192%	$70.468	$70.47	$70.45	$70.50
Purchase #4	$11.39	13.694%	$12.9497	$12.95	$12.95	$12.90
Purchase #5	$50.86	3.431%	$52.605	$52.61	$52.60	$52.60
Purchase #6	$104.50	10.488%	$115.46	$115.46	$115.45	$115.50
Purchase #7	$156.68	11.800%	$175.1682	$175.17	$175.15	$175.20
7 purchase totals =	$670.46		$724.2240	$724.23	$724.15	$724.30