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	$236.50	10.344%	$260.9636	$260.96	$260.95	$261.00
Purchase #2	$173.78	13.266%	$196.8337	$196.83	$196.85	$196.80
Purchase #3	$118.41	6.621%	$126.2499	$126.25	$126.25	$126.20
Purchase #4	$90.75	11.867%	$101.5193	$101.52	$101.50	$101.50
Purchase #5	$108.88	3.507%	$112.6984	$112.70	$112.70	$112.70
Purchase #6	$167.98	5.209%	$176.7301	$176.73	$176.75	$176.70
Purchase #7	$217.72	13.733%	$247.6195	$247.62	$247.60	$247.60
7 purchase totals =	$1,114.02		$1,222.6145	$1,222.61	$1,222.60	$1,222.50