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	$66.97	3.559%	$69.3535	$69.35	$69.35	$69.40
Purchase #2	$122.69	3.234%	$126.6578	$126.66	$126.65	$126.70
Purchase #3	$191.40	4.282%	$199.5957	$199.60	$199.60	$199.60
Purchase #4	$101.85	10.248%	$112.2876	$112.29	$112.30	$112.30
Purchase #5	$109.98	13.772%	$125.1264	$125.13	$125.15	$125.10
Purchase #6	$103.84	7.719%	$111.8554	$111.86	$111.85	$111.90
Purchase #7	$19.31	11.848%	$21.5978	$21.60	$21.60	$21.60
7 purchase totals =	$716.04		$766.4742	$766.49	$766.50	$766.60