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	$172.42	7.719%	$185.7291	$185.73	$185.75	$185.70
Purchase #2	$139.69	13.237%	$158.1808	$158.18	$158.20	$158.20
Purchase #3	$118.66	7.624%	$127.7066	$127.71	$127.70	$127.70
Purchase #4	$79.35	11.763%	$88.6839	$88.68	$88.70	$88.70
Purchase #5	$117.95	7.675%	$127.0027	$127.00	$127.00	$127.00
Purchase #6	$71.37	11.553%	$79.6154	$79.62	$79.60	$79.60
Purchase #7	$234.28	7.524%	$251.9072	$251.91	$251.90	$251.90
7 purchase totals =	$933.72		$1,018.8257	$1,018.83	$1,018.85	$1,018.80