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	$13.64	7.279%	$14.6329	$14.63	$14.65	$14.60
Purchase #2	$230.46	10.786%	$255.3174	$255.32	$255.30	$255.30
Purchase #3	$31.36	10.836%	$34.7582	$34.76	$34.75	$34.80
Purchase #4	$82.75	8.494%	$89.7788	$89.78	$89.80	$89.80
Purchase #5	$212.66	9.671%	$233.2263	$233.23	$233.25	$233.20
Purchase #6	$191.79	9.727%	$210.4454	$210.45	$210.45	$210.40
Purchase #7	$42.55	4.807%	$44.5954	$44.60	$44.60	$44.60
7 purchase totals =	$805.21		$882.7544	$882.77	$882.80	$882.70