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	$57.30	11.450%	$63.8609	$63.86	$63.85	$63.90
Purchase #2	$146.51	10.424%	$161.7822	$161.78	$161.80	$161.80
Purchase #3	$76.30	9.468%	$83.5241	$83.52	$83.50	$83.50
Purchase #4	$222.78	4.646%	$233.1304	$233.13	$233.15	$233.10
Purchase #5	$86.75	4.305%	$90.4846	$90.48	$90.50	$90.50
Purchase #6	$5.35	5.717%	$5.6559	$5.66	$5.65	$5.70
Purchase #7	$34.80	11.521%	$38.8093	$38.81	$38.80	$38.80
7 purchase totals =	$629.79		$677.2474	$677.24	$677.25	$677.30