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	$40.81	13.620%	$46.3683	$46.37	$46.35	$46.40
Purchase #2	$112.83	4.720%	$118.1556	$118.16	$118.15	$118.20
Purchase #3	$109.93	7.545%	$118.2242	$118.22	$118.20	$118.20
Purchase #4	$188.76	5.572%	$199.2777	$199.28	$199.30	$199.30
Purchase #5	$45.56	13.222%	$51.5839	$51.58	$51.60	$51.60
Purchase #6	$142.33	7.106%	$152.444	$152.44	$152.45	$152.40
Purchase #7	$101.90	9.521%	$111.6019	$111.60	$111.60	$111.60
7 purchase totals =	$742.12		$797.6556	$797.65	$797.65	$797.70