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	$46.60	11.867%	$52.13	$52.13	$52.15	$52.10
Purchase #2	$61.85	7.571%	$66.5327	$66.53	$66.55	$66.50
Purchase #3	$50.66	5.371%	$53.3809	$53.38	$53.40	$53.40
Purchase #4	$36.89	9.433%	$40.3698	$40.37	$40.35	$40.40
Purchase #5	$219.27	5.284%	$230.8562	$230.86	$230.85	$230.90
Purchase #6	$44.99	12.103%	$50.4351	$50.44	$50.45	$50.40
Purchase #7	$197.59	8.391%	$214.1698	$214.17	$214.15	$214.20
7 purchase totals =	$657.85		$707.8745	$707.88	$707.90	$707.90