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	$154.25	10.549%	$170.5218	$170.52	$170.50	$170.50
Purchase #2	$45.69	4.325%	$47.6661	$47.67	$47.65	$47.70
Purchase #3	$229.56	8.871%	$249.9243	$249.92	$249.90	$249.90
Purchase #4	$159.98	11.399%	$178.2161	$178.22	$178.20	$178.20
Purchase #5	$158.76	5.659%	$167.7442	$167.74	$167.75	$167.70
Purchase #6	$236.89	7.838%	$255.4574	$255.46	$255.45	$255.50
Purchase #7	$130.76	11.754%	$146.1295	$146.13	$146.15	$146.10
7 purchase totals =	$1,115.89		$1,215.6594	$1,215.66	$1,215.60	$1,215.60