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	$241.45	4.135%	$251.434	$251.43	$251.45	$251.40
Purchase #2	$142.86	6.286%	$151.8402	$151.84	$151.85	$151.80
Purchase #3	$20.73	3.557%	$21.4674	$21.47	$21.45	$21.50
Purchase #4	$244.32	11.320%	$271.977	$271.98	$272.00	$272.00
Purchase #5	$44.93	12.478%	$50.5364	$50.54	$50.55	$50.50
Purchase #6	$118.26	12.671%	$133.2447	$133.24	$133.25	$133.20
Purchase #7	$236.51	8.195%	$255.892	$255.89	$255.90	$255.90
7 purchase totals =	$1,049.06		$1,136.3917	$1,136.39	$1,136.45	$1,136.30