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	$160.42	7.776%	$172.8943	$172.89	$172.90	$172.90
Purchase #2	$84.39	5.773%	$89.2618	$89.26	$89.25	$89.30
Purchase #3	$192.96	7.522%	$207.4745	$207.47	$207.45	$207.50
Purchase #4	$108.42	7.445%	$116.4919	$116.49	$116.50	$116.50
Purchase #5	$186.60	7.487%	$200.5707	$200.57	$200.55	$200.60
Purchase #6	$48.99	8.696%	$53.2502	$53.25	$53.25	$53.30
Purchase #7	$95.66	12.114%	$107.2483	$107.25	$107.25	$107.20
7 purchase totals =	$877.44		$947.1917	$947.18	$947.15	$947.30