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	$63.86	13.335%	$72.3757	$72.38	$72.40	$72.40
Purchase #2	$180.49	6.744%	$192.6622	$192.66	$192.65	$192.70
Purchase #3	$143.66	5.748%	$151.9176	$151.92	$151.90	$151.90
Purchase #4	$55.26	9.127%	$60.3036	$60.30	$60.30	$60.30
Purchase #5	$230.78	12.232%	$259.009	$259.01	$259.00	$259.00
Purchase #6	$26.65	8.255%	$28.85	$28.85	$28.85	$28.90
Purchase #7	$20.82	4.792%	$21.8177	$21.82	$21.80	$21.80
7 purchase totals =	$721.52		$786.9358	$786.94	$786.90	$787.00