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	$237.62	12.233%	$266.6881	$266.69	$266.70	$266.70
Purchase #2	$43.56	13.602%	$49.485	$49.49	$49.50	$49.50
Purchase #3	$30.28	7.409%	$32.5234	$32.52	$32.50	$32.50
Purchase #4	$220.55	13.383%	$250.0662	$250.07	$250.05	$250.10
Purchase #5	$39.60	10.236%	$43.6535	$43.65	$43.65	$43.70
Purchase #6	$231.40	5.655%	$244.4857	$244.49	$244.50	$244.50
Purchase #7	$99.83	11.233%	$111.0439	$111.04	$111.05	$111.00
7 purchase totals =	$902.84		$997.9458	$997.95	$997.95	$998.00