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	$42.46	6.348%	$45.1554	$45.16	$45.15	$45.20
Purchase #2	$152.58	10.428%	$168.491	$168.49	$168.50	$168.50
Purchase #3	$111.56	13.131%	$126.2089	$126.21	$126.20	$126.20
Purchase #4	$134.92	5.110%	$141.8144	$141.81	$141.80	$141.80
Purchase #5	$84.85	3.224%	$87.5856	$87.59	$87.60	$87.60
Purchase #6	$105.87	6.379%	$112.6234	$112.62	$112.60	$112.60
Purchase #7	$198.98	7.779%	$214.4587	$214.46	$214.45	$214.50
7 purchase totals =	$831.22		$896.3374	$896.34	$896.30	$896.40