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	$232.83	6.737%	$248.5158	$248.52	$248.50	$248.50
Purchase #2	$75.61	3.336%	$78.1323	$78.13	$78.15	$78.10
Purchase #3	$237.84	4.162%	$247.7389	$247.74	$247.75	$247.70
Purchase #4	$148.60	3.290%	$153.4889	$153.49	$153.50	$153.50
Purchase #5	$105.95	7.260%	$113.642	$113.64	$113.65	$113.60
Purchase #6	$55.57	7.106%	$59.5188	$59.52	$59.50	$59.50
Purchase #7	$97.52	13.869%	$111.045	$111.05	$111.05	$111.00
7 purchase totals =	$953.92		$1,012.0817	$1,012.09	$1,012.10	$1,011.90