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	$79.70	10.143%	$87.784	$87.78	$87.80	$87.80
Purchase #2	$226.40	13.586%	$257.1587	$257.16	$257.15	$257.20
Purchase #3	$27.79	10.671%	$30.7555	$30.76	$30.75	$30.80
Purchase #4	$48.62	8.736%	$52.8674	$52.87	$52.85	$52.90
Purchase #5	$74.42	10.607%	$82.3137	$82.31	$82.30	$82.30
Purchase #6	$83.52	3.538%	$86.4749	$86.47	$86.45	$86.50
Purchase #7	$117.50	8.591%	$127.5944	$127.59	$127.60	$127.60
7 purchase totals =	$657.95		$724.9486	$724.94	$724.90	$725.10