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	$146.37	6.349%	$155.663	$155.66	$155.65	$155.70
Purchase #2	$9.95	4.617%	$10.4094	$10.41	$10.40	$10.40
Purchase #3	$48.35	5.762%	$51.1359	$51.14	$51.15	$51.10
Purchase #4	$238.40	12.111%	$267.2726	$267.27	$267.25	$267.30
Purchase #5	$72.45	3.185%	$74.7575	$74.76	$74.75	$74.80
Purchase #6	$87.42	3.341%	$90.3407	$90.34	$90.35	$90.30
Purchase #7	$71.29	13.407%	$80.8479	$80.85	$80.85	$80.80
7 purchase totals =	$674.23		$730.4270	$730.43	$730.40	$730.40