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	$136.40	13.763%	$155.1727	$155.17	$155.15	$155.20
Purchase #2	$54.80	12.449%	$61.6221	$61.62	$61.60	$61.60
Purchase #3	$232.94	9.710%	$255.5585	$255.56	$255.55	$255.60
Purchase #4	$51.64	4.757%	$54.0965	$54.10	$54.10	$54.10
Purchase #5	$215.90	6.688%	$230.3394	$230.34	$230.35	$230.30
Purchase #6	$204.53	13.192%	$231.5116	$231.51	$231.50	$231.50
Purchase #7	$26.86	8.521%	$29.1487	$29.15	$29.15	$29.10
7 purchase totals =	$923.07		$1,017.4495	$1,017.45	$1,017.40	$1,017.40