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	$144.72	12.419%	$162.6928	$162.69	$162.70	$162.70
Purchase #2	$105.87	10.141%	$116.6063	$116.61	$116.60	$116.60
Purchase #3	$172.87	3.598%	$179.0899	$179.09	$179.10	$179.10
Purchase #4	$212.28	13.793%	$241.5598	$241.56	$241.55	$241.60
Purchase #5	$132.81	6.301%	$141.1784	$141.18	$141.20	$141.20
Purchase #6	$135.87	4.274%	$141.6771	$141.68	$141.70	$141.70
Purchase #7	$119.65	11.593%	$133.521	$133.52	$133.50	$133.50
7 purchase totals =	$1,024.07		$1,116.3253	$1,116.33	$1,116.35	$1,116.40