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	$150.44	7.598%	$161.8704	$161.87	$161.85	$161.90
Purchase #2	$117.66	8.530%	$127.6964	$127.70	$127.70	$127.70
Purchase #3	$145.40	3.353%	$150.2753	$150.28	$150.30	$150.30
Purchase #4	$16.70	7.635%	$17.975	$17.98	$18.00	$18.00
Purchase #5	$106.87	9.376%	$116.8901	$116.89	$116.90	$116.90
Purchase #6	$156.83	10.251%	$172.9066	$172.91	$172.90	$172.90
Purchase #7	$246.92	9.722%	$270.9256	$270.93	$270.95	$270.90
7 purchase totals =	$940.82		$1,018.5394	$1,018.56	$1,018.60	$1,018.60