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	$148.72	6.796%	$158.827	$158.83	$158.85	$158.80
Purchase #2	$103.69	10.711%	$114.7962	$114.80	$114.80	$114.80
Purchase #3	$238.31	7.627%	$256.4859	$256.49	$256.50	$256.50
Purchase #4	$50.70	5.555%	$53.5164	$53.52	$53.50	$53.50
Purchase #5	$130.54	11.467%	$145.509	$145.51	$145.50	$145.50
Purchase #6	$96.25	9.544%	$105.4361	$105.44	$105.45	$105.40
Purchase #7	$223.60	7.295%	$239.9116	$239.91	$239.90	$239.90
7 purchase totals =	$991.81		$1,074.4822	$1,074.50	$1,074.50	$1,074.40