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	$160.43	6.406%	$170.7071	$170.71	$170.70	$170.70
Purchase #2	$221.49	6.781%	$236.5092	$236.51	$236.50	$236.50
Purchase #3	$89.52	11.391%	$99.7172	$99.72	$99.70	$99.70
Purchase #4	$172.43	8.158%	$186.4968	$186.50	$186.50	$186.50
Purchase #5	$158.56	8.626%	$172.2374	$172.24	$172.25	$172.20
Purchase #6	$166.66	6.397%	$177.3212	$177.32	$177.30	$177.30
Purchase #7	$22.36	5.523%	$23.5949	$23.59	$23.60	$23.60
7 purchase totals =	$991.45		$1,066.5838	$1,066.59	$1,066.55	$1,066.50