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	$200.32	5.638%	$211.614	$211.61	$211.60	$211.60
Purchase #2	$214.80	11.477%	$239.4526	$239.45	$239.45	$239.50
Purchase #3	$126.56	8.474%	$137.2847	$137.28	$137.30	$137.30
Purchase #4	$69.52	12.666%	$78.3254	$78.33	$78.35	$78.30
Purchase #5	$9.68	6.533%	$10.3124	$10.31	$10.30	$10.30
Purchase #6	$112.30	13.545%	$127.511	$127.51	$127.50	$127.50
Purchase #7	$16.85	3.854%	$17.4994	$17.50	$17.50	$17.50
7 purchase totals =	$750.03		$821.9995	$821.99	$822.00	$822.00