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	$131.98	10.538%	$145.8881	$145.89	$145.90	$145.90
Purchase #2	$137.90	6.244%	$146.5105	$146.51	$146.50	$146.50
Purchase #3	$58.77	8.178%	$63.5762	$63.58	$63.60	$63.60
Purchase #4	$31.51	7.375%	$33.8339	$33.83	$33.85	$33.80
Purchase #5	$176.65	3.840%	$183.4334	$183.43	$183.45	$183.40
Purchase #6	$43.97	9.339%	$48.0764	$48.08	$48.10	$48.10
Purchase #7	$72.44	8.172%	$78.3598	$78.36	$78.35	$78.40
7 purchase totals =	$653.22		$699.6783	$699.68	$699.75	$699.70