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	$134.65	8.656%	$146.3053	$146.31	$146.30	$146.30
Purchase #2	$162.72	5.809%	$172.1724	$172.17	$172.15	$172.20
Purchase #3	$35.67	7.573%	$38.3713	$38.37	$38.35	$38.40
Purchase #4	$77.78	7.583%	$83.6781	$83.68	$83.70	$83.70
Purchase #5	$49.81	5.570%	$52.5844	$52.58	$52.60	$52.60
Purchase #6	$142.83	11.639%	$159.454	$159.45	$159.45	$159.50
Purchase #7	$35.62	9.163%	$38.8839	$38.88	$38.90	$38.90
7 purchase totals =	$639.08		$691.4494	$691.44	$691.45	$691.60