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	$210.88	11.448%	$235.0215	$235.02	$235.00	$235.00
Purchase #2	$45.87	8.748%	$49.8827	$49.88	$49.90	$49.90
Purchase #3	$65.28	10.289%	$71.9967	$72.00	$72.00	$72.00
Purchase #4	$167.69	10.596%	$185.4584	$185.46	$185.45	$185.50
Purchase #5	$94.50	6.434%	$100.5801	$100.58	$100.60	$100.60
Purchase #6	$159.42	3.189%	$164.5039	$164.50	$164.50	$164.50
Purchase #7	$7.52	10.157%	$8.2838	$8.28	$8.30	$8.30
7 purchase totals =	$751.16		$815.7271	$815.72	$815.75	$815.80