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	$188.48	10.613%	$208.4834	$208.48	$208.50	$208.50
Purchase #2	$85.46	11.255%	$95.0785	$95.08	$95.10	$95.10
Purchase #3	$148.51	3.345%	$153.4777	$153.48	$153.50	$153.50
Purchase #4	$12.85	3.232%	$13.2653	$13.27	$13.25	$13.30
Purchase #5	$183.86	6.389%	$195.6068	$195.61	$195.60	$195.60
Purchase #6	$24.77	10.860%	$27.46	$27.46	$27.45	$27.50
Purchase #7	$14.82	7.274%	$15.898	$15.90	$15.90	$15.90
7 purchase totals =	$658.75		$709.2697	$709.28	$709.30	$709.40