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	$240.32	10.823%	$266.3298	$266.33	$266.35	$266.30
Purchase #2	$55.32	13.190%	$62.6167	$62.62	$62.60	$62.60
Purchase #3	$100.78	10.802%	$111.6663	$111.67	$111.65	$111.70
Purchase #4	$247.85	3.316%	$256.0687	$256.07	$256.05	$256.10
Purchase #5	$242.26	4.548%	$253.278	$253.28	$253.30	$253.30
Purchase #6	$220.67	12.589%	$248.4501	$248.45	$248.45	$248.50
Purchase #7	$32.51	8.809%	$35.3738	$35.37	$35.35	$35.40
7 purchase totals =	$1,139.71		$1,233.7834	$1,233.79	$1,233.75	$1,233.90