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	$249.61	5.571%	$263.5158	$263.52	$263.50	$263.50
Purchase #2	$154.57	4.288%	$161.198	$161.20	$161.20	$161.20
Purchase #3	$247.86	11.721%	$276.9117	$276.91	$276.90	$276.90
Purchase #4	$135.98	5.391%	$143.3107	$143.31	$143.30	$143.30
Purchase #5	$88.51	13.838%	$100.758	$100.76	$100.75	$100.80
Purchase #6	$111.70	13.835%	$127.1537	$127.15	$127.15	$127.20
Purchase #7	$133.89	13.237%	$151.613	$151.61	$151.60	$151.60
7 purchase totals =	$1,122.12		$1,224.4609	$1,224.46	$1,224.40	$1,224.50