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	$64.39	7.642%	$69.3107	$69.31	$69.30	$69.30
Purchase #2	$101.29	11.497%	$112.9353	$112.94	$112.95	$112.90
Purchase #3	$146.54	9.500%	$160.4613	$160.46	$160.45	$160.50
Purchase #4	$188.53	6.509%	$200.8014	$200.80	$200.80	$200.80
Purchase #5	$176.43	6.344%	$187.6227	$187.62	$187.60	$187.60
Purchase #6	$238.45	7.708%	$256.8297	$256.83	$256.85	$256.80
Purchase #7	$88.47	13.602%	$100.5037	$100.50	$100.50	$100.50
7 purchase totals =	$1,004.10		$1,088.4648	$1,088.46	$1,088.45	$1,088.40