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	$103.40	8.325%	$112.0081	$112.01	$112.00	$112.00
Purchase #2	$18.92	8.120%	$20.4563	$20.46	$20.45	$20.50
Purchase #3	$144.79	9.485%	$158.5233	$158.52	$158.50	$158.50
Purchase #4	$13.63	5.137%	$14.3302	$14.33	$14.35	$14.30
Purchase #5	$18.26	13.602%	$20.7437	$20.74	$20.75	$20.70
Purchase #6	$153.60	7.859%	$165.6714	$165.67	$165.65	$165.70
Purchase #7	$154.85	8.225%	$167.5864	$167.59	$167.60	$167.60
7 purchase totals =	$607.45		$659.3194	$659.32	$659.30	$659.30