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	$174.52	4.684%	$182.6945	$182.69	$182.70	$182.70
Purchase #2	$145.52	5.538%	$153.5789	$153.58	$153.60	$153.60
Purchase #3	$9.91	10.501%	$10.9506	$10.95	$10.95	$11.00
Purchase #4	$192.39	8.409%	$208.5681	$208.57	$208.55	$208.60
Purchase #5	$114.82	7.770%	$123.7415	$123.74	$123.75	$123.70
Purchase #6	$95.66	4.815%	$100.266	$100.27	$100.25	$100.30
Purchase #7	$167.53	7.480%	$180.0612	$180.06	$180.05	$180.10
7 purchase totals =	$900.35		$959.8608	$959.86	$959.85	$960.00