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	$21.91	10.733%	$24.2616	$24.26	$24.25	$24.30
Purchase #2	$78.31	9.439%	$85.7017	$85.70	$85.70	$85.70
Purchase #3	$238.49	10.535%	$263.6149	$263.61	$263.60	$263.60
Purchase #4	$142.53	11.495%	$158.9138	$158.91	$158.90	$158.90
Purchase #5	$167.87	11.635%	$187.4017	$187.40	$187.40	$187.40
Purchase #6	$100.64	5.468%	$106.143	$106.14	$106.15	$106.10
Purchase #7	$132.40	10.795%	$146.6926	$146.69	$146.70	$146.70
7 purchase totals =	$882.15		$972.7293	$972.71	$972.70	$972.70