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	$193.81	11.494%	$216.0865	$216.09	$216.10	$216.10
Purchase #2	$235.41	12.806%	$265.5566	$265.56	$265.55	$265.60
Purchase #3	$48.68	12.208%	$54.6229	$54.62	$54.60	$54.60
Purchase #4	$97.31	8.786%	$105.8597	$105.86	$105.85	$105.90
Purchase #5	$149.85	10.242%	$165.1976	$165.20	$165.20	$165.20
Purchase #6	$70.94	6.383%	$75.4681	$75.47	$75.45	$75.50
Purchase #7	$170.56	7.739%	$183.7596	$183.76	$183.75	$183.80
7 purchase totals =	$966.56		$1,066.5510	$1,066.56	$1,066.50	$1,066.70