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	$143.52	10.533%	$158.637	$158.64	$158.65	$158.60
Purchase #2	$180.29	8.730%	$196.0293	$196.03	$196.05	$196.00
Purchase #3	$103.44	13.309%	$117.2068	$117.21	$117.20	$117.20
Purchase #4	$60.76	9.485%	$66.5231	$66.52	$66.50	$66.50
Purchase #5	$233.61	4.159%	$243.3258	$243.33	$243.35	$243.30
Purchase #6	$223.59	4.395%	$233.4168	$233.42	$233.40	$233.40
Purchase #7	$223.79	5.200%	$235.4271	$235.43	$235.45	$235.40
7 purchase totals =	$1,169.00		$1,250.5659	$1,250.58	$1,250.60	$1,250.40