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	$177.91	10.206%	$196.0675	$196.07	$196.05	$196.10
Purchase #2	$146.33	13.116%	$165.5226	$165.52	$165.50	$165.50
Purchase #3	$12.97	6.540%	$13.8182	$13.82	$13.80	$13.80
Purchase #4	$226.67	8.846%	$246.7212	$246.72	$246.70	$246.70
Purchase #5	$217.69	10.288%	$240.0859	$240.09	$240.10	$240.10
Purchase #6	$11.49	3.559%	$11.8989	$11.90	$11.90	$11.90
Purchase #7	$198.74	13.274%	$225.1207	$225.12	$225.10	$225.10
7 purchase totals =	$991.80		$1,099.2350	$1,099.24	$1,099.15	$1,099.20