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	$143.87	6.379%	$153.0475	$153.05	$153.05	$153.00
Purchase #2	$233.65	3.514%	$241.8605	$241.86	$241.85	$241.90
Purchase #3	$47.77	12.733%	$53.8526	$53.85	$53.85	$53.90
Purchase #4	$186.59	9.163%	$203.6872	$203.69	$203.70	$203.70
Purchase #5	$55.61	6.861%	$59.4254	$59.43	$59.45	$59.40
Purchase #6	$118.71	8.177%	$128.4169	$128.42	$128.40	$128.40
Purchase #7	$65.32	7.614%	$70.2935	$70.29	$70.30	$70.30
7 purchase totals =	$851.52		$910.5836	$910.59	$910.60	$910.60