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	$132.86	3.497%	$137.5061	$137.51	$137.50	$137.50
Purchase #2	$159.45	4.420%	$166.4977	$166.50	$166.50	$166.50
Purchase #3	$183.38	6.237%	$194.8174	$194.82	$194.80	$194.80
Purchase #4	$240.28	9.701%	$263.5896	$263.59	$263.60	$263.60
Purchase #5	$51.47	4.144%	$53.6029	$53.60	$53.60	$53.60
Purchase #6	$35.65	6.388%	$37.9273	$37.93	$37.95	$37.90
Purchase #7	$207.93	3.233%	$214.6524	$214.65	$214.65	$214.70
7 purchase totals =	$1,011.02		$1,068.5934	$1,068.60	$1,068.60	$1,068.60