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	$150.75	10.496%	$166.5727	$166.57	$166.55	$166.60
Purchase #2	$165.90	4.543%	$173.4368	$173.44	$173.45	$173.40
Purchase #3	$63.32	4.325%	$66.0586	$66.06	$66.05	$66.10
Purchase #4	$106.87	10.143%	$117.7098	$117.71	$117.70	$117.70
Purchase #5	$56.46	8.735%	$61.3918	$61.39	$61.40	$61.40
Purchase #6	$178.42	6.404%	$189.846	$189.85	$189.85	$189.80
Purchase #7	$216.50	12.526%	$243.6188	$243.62	$243.60	$243.60
7 purchase totals =	$938.22		$1,018.6345	$1,018.64	$1,018.60	$1,018.60