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	$159.25	12.135%	$178.575	$178.58	$178.60	$178.60
Purchase #2	$140.38	4.358%	$146.4978	$146.50	$146.50	$146.50
Purchase #3	$179.60	11.202%	$199.7188	$199.72	$199.70	$199.70
Purchase #4	$190.37	13.251%	$215.5959	$215.60	$215.60	$215.60
Purchase #5	$52.51	4.703%	$54.9795	$54.98	$55.00	$55.00
Purchase #6	$173.25	9.866%	$190.3428	$190.34	$190.35	$190.30
Purchase #7	$108.49	3.612%	$112.4087	$112.41	$112.40	$112.40
7 purchase totals =	$1,003.85		$1,098.1185	$1,098.13	$1,098.15	$1,098.10