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	$177.52	10.463%	$196.0939	$196.09	$196.10	$196.10
Purchase #2	$193.89	5.802%	$205.1395	$205.14	$205.15	$205.10
Purchase #3	$179.46	10.235%	$197.8277	$197.83	$197.85	$197.80
Purchase #4	$235.87	10.762%	$261.2543	$261.25	$261.25	$261.30
Purchase #5	$48.63	12.336%	$54.629	$54.63	$54.65	$54.60
Purchase #6	$130.52	11.128%	$145.0443	$145.04	$145.05	$145.00
Purchase #7	$79.88	13.439%	$90.6151	$90.62	$90.60	$90.60
7 purchase totals =	$1,045.77		$1,150.6038	$1,150.60	$1,150.65	$1,150.50