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	$107.81	4.350%	$112.4997	$112.50	$112.50	$112.50
Purchase #2	$98.33	5.859%	$104.0912	$104.09	$104.10	$104.10
Purchase #3	$89.90	11.429%	$100.1747	$100.17	$100.15	$100.20
Purchase #4	$48.92	12.317%	$54.9455	$54.95	$54.95	$54.90
Purchase #5	$15.42	11.752%	$17.2322	$17.23	$17.25	$17.20
Purchase #6	$232.85	9.335%	$254.5865	$254.59	$254.60	$254.60
Purchase #7	$22.31	7.539%	$23.992	$23.99	$24.00	$24.00
7 purchase totals =	$615.54		$667.5218	$667.52	$667.55	$667.50