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	$105.59	6.602%	$112.5611	$112.56	$112.55	$112.60
Purchase #2	$27.49	8.762%	$29.8987	$29.90	$29.90	$29.90
Purchase #3	$132.31	12.309%	$148.596	$148.60	$148.60	$148.60
Purchase #4	$241.35	11.582%	$269.3032	$269.30	$269.30	$269.30
Purchase #5	$53.32	5.584%	$56.2974	$56.30	$56.30	$56.30
Purchase #6	$97.59	5.722%	$103.1741	$103.17	$103.15	$103.20
Purchase #7	$60.66	13.162%	$68.6441	$68.64	$68.65	$68.60
7 purchase totals =	$718.31		$788.4746	$788.47	$788.45	$788.50