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	$153.85	12.719%	$173.4182	$173.42	$173.40	$173.40
Purchase #2	$240.62	13.194%	$272.3674	$272.37	$272.35	$272.40
Purchase #3	$160.47	3.434%	$165.9805	$165.98	$166.00	$166.00
Purchase #4	$133.31	5.830%	$141.082	$141.08	$141.10	$141.10
Purchase #5	$114.75	6.503%	$122.2122	$122.21	$122.20	$122.20
Purchase #6	$120.28	5.814%	$127.2731	$127.27	$127.25	$127.30
Purchase #7	$156.26	10.435%	$172.5657	$172.57	$172.55	$172.60
7 purchase totals =	$1,079.54		$1,174.8991	$1,174.90	$1,174.85	$1,175.00