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	$140.74	11.174%	$156.4663	$156.47	$156.45	$156.50
Purchase #2	$49.51	8.121%	$53.5307	$53.53	$53.55	$53.50
Purchase #3	$58.99	10.240%	$65.0306	$65.03	$65.05	$65.00
Purchase #4	$51.34	6.158%	$54.5015	$54.50	$54.50	$54.50
Purchase #5	$83.66	8.103%	$90.439	$90.44	$90.45	$90.40
Purchase #6	$81.35	11.130%	$90.4043	$90.40	$90.40	$90.40
Purchase #7	$193.32	7.247%	$207.3299	$207.33	$207.35	$207.30
7 purchase totals =	$658.91		$717.7023	$717.70	$717.75	$717.60