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	$31.38	10.228%	$34.5895	$34.59	$34.60	$34.60
Purchase #2	$142.53	6.308%	$151.5208	$151.52	$151.50	$151.50
Purchase #3	$53.88	13.370%	$61.0838	$61.08	$61.10	$61.10
Purchase #4	$92.66	4.336%	$96.6777	$96.68	$96.70	$96.70
Purchase #5	$152.31	13.700%	$173.1765	$173.18	$173.20	$173.20
Purchase #6	$228.56	8.257%	$247.4322	$247.43	$247.45	$247.40
Purchase #7	$18.63	5.151%	$19.5896	$19.59	$19.60	$19.60
7 purchase totals =	$719.95		$784.0701	$784.07	$784.15	$784.10