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	$158.45	4.551%	$165.6611	$165.66	$165.65	$165.70
Purchase #2	$53.90	9.732%	$59.1455	$59.15	$59.15	$59.10
Purchase #3	$243.98	11.164%	$271.2179	$271.22	$271.20	$271.20
Purchase #4	$101.70	3.760%	$105.5239	$105.52	$105.50	$105.50
Purchase #5	$64.64	11.409%	$72.0148	$72.01	$72.00	$72.00
Purchase #6	$126.72	4.766%	$132.7595	$132.76	$132.75	$132.80
Purchase #7	$147.41	9.466%	$161.3638	$161.36	$161.35	$161.40
7 purchase totals =	$896.80		$967.6865	$967.68	$967.60	$967.70