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	$240.44	5.121%	$252.7529	$252.75	$252.75	$252.80
Purchase #2	$107.51	3.454%	$111.2234	$111.22	$111.20	$111.20
Purchase #3	$93.59	6.325%	$99.5096	$99.51	$99.50	$99.50
Purchase #4	$223.62	4.874%	$234.5192	$234.52	$234.50	$234.50
Purchase #5	$99.35	9.606%	$108.8936	$108.89	$108.90	$108.90
Purchase #6	$78.41	6.428%	$83.4502	$83.45	$83.45	$83.50
Purchase #7	$241.56	7.211%	$258.9789	$258.98	$259.00	$259.00
7 purchase totals =	$1,084.48		$1,149.3278	$1,149.32	$1,149.30	$1,149.40