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	$249.31	3.234%	$257.3727	$257.37	$257.35	$257.40
Purchase #2	$148.65	6.568%	$158.4133	$158.41	$158.40	$158.40
Purchase #3	$153.83	5.658%	$162.5337	$162.53	$162.55	$162.50
Purchase #4	$204.68	12.624%	$230.5188	$230.52	$230.50	$230.50
Purchase #5	$62.88	13.715%	$71.504	$71.50	$71.50	$71.50
Purchase #6	$112.45	3.273%	$116.1305	$116.13	$116.15	$116.10
Purchase #7	$110.91	6.477%	$118.0936	$118.09	$118.10	$118.10
7 purchase totals =	$1,042.71		$1,114.5666	$1,114.55	$1,114.55	$1,114.50