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	$185.89	4.793%	$194.7997	$194.80	$194.80	$194.80
Purchase #2	$146.55	5.368%	$154.4168	$154.42	$154.40	$154.40
Purchase #3	$13.69	9.275%	$14.9597	$14.96	$14.95	$15.00
Purchase #4	$138.69	10.245%	$152.8988	$152.90	$152.90	$152.90
Purchase #5	$241.99	3.679%	$250.8928	$250.89	$250.90	$250.90
Purchase #6	$83.52	3.694%	$86.6052	$86.61	$86.60	$86.60
Purchase #7	$11.44	11.182%	$12.7192	$12.72	$12.70	$12.70
7 purchase totals =	$821.77		$867.2922	$867.30	$867.25	$867.30