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	$134.39	7.772%	$144.8348	$144.83	$144.85	$144.80
Purchase #2	$6.91	9.697%	$7.5801	$7.58	$7.60	$7.60
Purchase #3	$62.49	5.183%	$65.7289	$65.73	$65.75	$65.70
Purchase #4	$20.83	6.129%	$22.1067	$22.11	$22.10	$22.10
Purchase #5	$101.76	9.222%	$111.1443	$111.14	$111.15	$111.10
Purchase #6	$54.28	4.859%	$56.9175	$56.92	$56.90	$56.90
Purchase #7	$100.45	3.314%	$103.7789	$103.78	$103.80	$103.80
7 purchase totals =	$481.11		$512.0912	$512.09	$512.15	$512.00