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	$241.35	10.191%	$265.946	$265.95	$265.95	$265.90
Purchase #2	$110.43	6.332%	$117.4224	$117.42	$117.40	$117.40
Purchase #3	$119.99	9.351%	$131.2103	$131.21	$131.20	$131.20
Purchase #4	$58.46	10.694%	$64.7117	$64.71	$64.70	$64.70
Purchase #5	$145.49	13.461%	$165.0744	$165.07	$165.05	$165.10
Purchase #6	$52.90	11.715%	$59.0972	$59.10	$59.10	$59.10
Purchase #7	$158.41	4.541%	$165.6034	$165.60	$165.60	$165.60
7 purchase totals =	$887.03		$969.0654	$969.06	$969.00	$969.00