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	$125.64	10.433%	$138.748	$138.75	$138.75	$138.70
Purchase #2	$57.73	9.399%	$63.156	$63.16	$63.15	$63.20
Purchase #3	$10.77	10.753%	$11.9281	$11.93	$11.95	$11.90
Purchase #4	$80.92	10.500%	$89.4166	$89.42	$89.40	$89.40
Purchase #5	$58.85	11.692%	$65.7307	$65.73	$65.75	$65.70
Purchase #6	$26.38	4.538%	$27.5771	$27.58	$27.60	$27.60
Purchase #7	$230.98	11.192%	$256.8313	$256.83	$256.85	$256.80
7 purchase totals =	$591.27		$653.3878	$653.40	$653.45	$653.30