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	$47.34	11.145%	$52.616	$52.62	$52.60	$52.60
Purchase #2	$67.95	5.856%	$71.9292	$71.93	$71.95	$71.90
Purchase #3	$99.40	6.201%	$105.5638	$105.56	$105.55	$105.60
Purchase #4	$31.48	7.675%	$33.8961	$33.90	$33.90	$33.90
Purchase #5	$61.74	3.393%	$63.8348	$63.83	$63.85	$63.80
Purchase #6	$145.65	8.748%	$158.3915	$158.39	$158.40	$158.40
Purchase #7	$94.40	6.487%	$100.5237	$100.52	$100.50	$100.50
7 purchase totals =	$547.96		$586.7551	$586.75	$586.75	$586.70