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	$226.41	8.702%	$246.1122	$246.11	$246.10	$246.10
Purchase #2	$89.37	5.422%	$94.2156	$94.22	$94.20	$94.20
Purchase #3	$90.68	3.337%	$93.706	$93.71	$93.70	$93.70
Purchase #4	$47.61	8.350%	$51.5854	$51.59	$51.60	$51.60
Purchase #5	$160.42	3.233%	$165.6064	$165.61	$165.60	$165.60
Purchase #6	$123.38	3.521%	$127.7242	$127.72	$127.70	$127.70
Purchase #7	$38.96	10.826%	$43.1778	$43.18	$43.20	$43.20
7 purchase totals =	$776.83		$822.1276	$822.14	$822.10	$822.10