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	$42.46	9.241%	$46.3837	$46.38	$46.40	$46.40
Purchase #2	$142.78	7.831%	$153.9611	$153.96	$153.95	$154.00
Purchase #3	$133.86	6.720%	$142.8554	$142.86	$142.85	$142.90
Purchase #4	$220.35	3.773%	$228.6638	$228.66	$228.65	$228.70
Purchase #5	$29.87	11.667%	$33.3549	$33.35	$33.35	$33.40
Purchase #6	$17.75	11.381%	$19.7701	$19.77	$19.75	$19.80
Purchase #7	$95.39	10.746%	$105.6406	$105.64	$105.65	$105.60
7 purchase totals =	$682.46		$730.6296	$730.62	$730.60	$730.80