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	$71.64	9.412%	$78.3828	$78.38	$78.40	$78.40
Purchase #2	$26.94	9.399%	$29.4721	$29.47	$29.45	$29.50
Purchase #3	$39.31	8.145%	$42.5118	$42.51	$42.50	$42.50
Purchase #4	$14.74	3.569%	$15.2661	$15.27	$15.25	$15.30
Purchase #5	$229.60	8.825%	$249.8622	$249.86	$249.85	$249.90
Purchase #6	$137.28	13.557%	$155.891	$155.89	$155.90	$155.90
Purchase #7	$133.59	10.806%	$148.0257	$148.03	$148.05	$148.00
7 purchase totals =	$653.10		$719.4117	$719.41	$719.40	$719.50