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	$146.28	8.464%	$158.6611	$158.66	$158.65	$158.70
Purchase #2	$118.26	5.313%	$124.5432	$124.54	$124.55	$124.50
Purchase #3	$110.98	10.729%	$122.887	$122.89	$122.90	$122.90
Purchase #4	$229.78	11.153%	$255.4074	$255.41	$255.40	$255.40
Purchase #5	$161.91	10.461%	$178.8474	$178.85	$178.85	$178.80
Purchase #6	$123.70	3.106%	$127.5421	$127.54	$127.55	$127.50
Purchase #7	$52.28	4.704%	$54.7393	$54.74	$54.75	$54.70
7 purchase totals =	$943.19		$1,022.6275	$1,022.63	$1,022.65	$1,022.50