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	$211.94	11.194%	$235.6646	$235.66	$235.65	$235.70
Purchase #2	$49.52	3.291%	$51.1497	$51.15	$51.15	$51.10
Purchase #3	$215.33	8.569%	$233.7816	$233.78	$233.80	$233.80
Purchase #4	$63.27	13.607%	$71.8791	$71.88	$71.90	$71.90
Purchase #5	$79.64	12.294%	$89.4309	$89.43	$89.45	$89.40
Purchase #6	$100.58	9.251%	$109.8847	$109.88	$109.90	$109.90
Purchase #7	$74.49	3.257%	$76.9161	$76.92	$76.90	$76.90
7 purchase totals =	$794.77		$868.7067	$868.70	$868.75	$868.70