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	$207.54	9.795%	$227.8685	$227.87	$227.85	$227.90
Purchase #2	$156.35	10.239%	$172.3587	$172.36	$172.35	$172.40
Purchase #3	$129.74	12.156%	$145.5112	$145.51	$145.50	$145.50
Purchase #4	$85.40	3.853%	$88.6905	$88.69	$88.70	$88.70
Purchase #5	$116.65	9.118%	$127.2861	$127.29	$127.30	$127.30
Purchase #6	$145.99	11.548%	$162.8489	$162.85	$162.85	$162.80
Purchase #7	$160.42	8.319%	$173.7653	$173.77	$173.75	$173.80
7 purchase totals =	$1,002.09		$1,098.3292	$1,098.34	$1,098.30	$1,098.40