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	$84.31	4.239%	$87.8839	$87.88	$87.90	$87.90
Purchase #2	$225.89	5.516%	$238.3501	$238.35	$238.35	$238.40
Purchase #3	$37.71	5.607%	$39.8244	$39.82	$39.80	$39.80
Purchase #4	$106.76	10.707%	$118.1908	$118.19	$118.20	$118.20
Purchase #5	$22.54	9.142%	$24.6006	$24.60	$24.60	$24.60
Purchase #6	$134.72	11.733%	$150.5267	$150.53	$150.55	$150.50
Purchase #7	$65.78	6.640%	$70.1478	$70.15	$70.15	$70.10
7 purchase totals =	$677.71		$729.5243	$729.52	$729.55	$729.50