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	$146.68	13.274%	$166.1503	$166.15	$166.15	$166.20
Purchase #2	$31.45	11.206%	$34.9743	$34.97	$34.95	$35.00
Purchase #3	$185.81	4.706%	$194.5542	$194.55	$194.55	$194.60
Purchase #4	$10.47	8.383%	$11.3477	$11.35	$11.35	$11.30
Purchase #5	$213.32	11.182%	$237.1734	$237.17	$237.15	$237.20
Purchase #6	$227.65	12.243%	$255.5212	$255.52	$255.50	$255.50
Purchase #7	$150.72	11.575%	$168.1658	$168.17	$168.15	$168.20
7 purchase totals =	$966.10		$1,067.8869	$1,067.88	$1,067.80	$1,068.00