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	$222.49	8.694%	$241.8333	$241.83	$241.85	$241.80
Purchase #2	$138.75	8.240%	$150.183	$150.18	$150.20	$150.20
Purchase #3	$209.80	3.652%	$217.4619	$217.46	$217.45	$217.50
Purchase #4	$10.58	3.563%	$10.957	$10.96	$10.95	$11.00
Purchase #5	$43.56	4.634%	$45.5786	$45.58	$45.60	$45.60
Purchase #6	$94.58	10.768%	$104.7644	$104.76	$104.75	$104.80
Purchase #7	$213.76	8.104%	$231.0831	$231.08	$231.10	$231.10
7 purchase totals =	$933.52		$1,001.8613	$1,001.85	$1,001.90	$1,002.00