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	$122.84	9.426%	$134.4189	$134.42	$134.40	$134.40
Purchase #2	$245.27	13.500%	$278.3815	$278.38	$278.40	$278.40
Purchase #3	$228.78	5.150%	$240.5622	$240.56	$240.55	$240.60
Purchase #4	$120.68	5.672%	$127.525	$127.53	$127.55	$127.50
Purchase #5	$118.61	11.782%	$132.5846	$132.58	$132.60	$132.60
Purchase #6	$65.51	9.492%	$71.7282	$71.73	$71.75	$71.70
Purchase #7	$60.70	9.724%	$66.6025	$66.60	$66.60	$66.60
7 purchase totals =	$962.39		$1,051.8029	$1,051.80	$1,051.85	$1,051.80