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	$235.94	4.139%	$245.7056	$245.71	$245.70	$245.70
Purchase #2	$50.59	10.293%	$55.7972	$55.80	$55.80	$55.80
Purchase #3	$42.68	9.188%	$46.6014	$46.60	$46.60	$46.60
Purchase #4	$50.76	7.105%	$54.3665	$54.37	$54.35	$54.40
Purchase #5	$85.43	5.129%	$89.8117	$89.81	$89.80	$89.80
Purchase #6	$126.79	5.307%	$133.5187	$133.52	$133.50	$133.50
Purchase #7	$101.81	10.121%	$112.1142	$112.11	$112.10	$112.10
7 purchase totals =	$694.00		$737.9153	$737.92	$737.85	$737.90