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	$161.66	10.491%	$178.6198	$178.62	$178.60	$178.60
Purchase #2	$148.27	11.335%	$165.0764	$165.08	$165.10	$165.10
Purchase #3	$229.55	8.139%	$248.2331	$248.23	$248.25	$248.20
Purchase #4	$242.89	4.855%	$254.6823	$254.68	$254.70	$254.70
Purchase #5	$99.31	12.158%	$111.3841	$111.38	$111.40	$111.40
Purchase #6	$42.41	11.717%	$47.3792	$47.38	$47.40	$47.40
Purchase #7	$53.28	4.461%	$55.6568	$55.66	$55.65	$55.70
7 purchase totals =	$977.37		$1,061.0317	$1,061.03	$1,061.10	$1,061.10