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	$118.78	12.852%	$134.0456	$134.05	$134.05	$134.00
Purchase #2	$17.68	4.574%	$18.4887	$18.49	$18.50	$18.50
Purchase #3	$29.89	13.510%	$33.9281	$33.93	$33.95	$33.90
Purchase #4	$25.98	4.528%	$27.1564	$27.16	$27.15	$27.20
Purchase #5	$56.91	10.385%	$62.8201	$62.82	$62.80	$62.80
Purchase #6	$153.70	13.635%	$174.657	$174.66	$174.65	$174.70
Purchase #7	$245.43	13.445%	$278.4281	$278.43	$278.45	$278.40
7 purchase totals =	$648.37		$729.5240	$729.54	$729.55	$729.50