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	$118.32	13.155%	$133.885	$133.89	$133.90	$133.90
Purchase #2	$165.89	6.513%	$176.6944	$176.69	$176.70	$176.70
Purchase #3	$93.51	12.490%	$105.1894	$105.19	$105.20	$105.20
Purchase #4	$137.32	5.303%	$144.6021	$144.60	$144.60	$144.60
Purchase #5	$109.71	4.463%	$114.6064	$114.61	$114.60	$114.60
Purchase #6	$121.43	8.188%	$131.3727	$131.37	$131.35	$131.40
Purchase #7	$249.75	10.540%	$276.0737	$276.07	$276.05	$276.10
7 purchase totals =	$995.93		$1,082.4237	$1,082.42	$1,082.40	$1,082.50