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	$155.75	8.128%	$168.4094	$168.41	$168.40	$168.40
Purchase #2	$172.27	6.416%	$183.3228	$183.32	$183.30	$183.30
Purchase #3	$11.53	4.850%	$12.0892	$12.09	$12.10	$12.10
Purchase #4	$231.97	13.300%	$262.822	$262.82	$262.80	$262.80
Purchase #5	$120.42	5.854%	$127.4694	$127.47	$127.45	$127.50
Purchase #6	$75.77	8.393%	$82.1294	$82.13	$82.15	$82.10
Purchase #7	$99.31	11.772%	$111.0008	$111.00	$111.00	$111.00
7 purchase totals =	$867.02		$947.2430	$947.24	$947.20	$947.20