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	$58.94	5.491%	$62.1764	$62.18	$62.20	$62.20
Purchase #2	$45.75	13.831%	$52.0777	$52.08	$52.10	$52.10
Purchase #3	$150.64	10.838%	$166.9664	$166.97	$166.95	$167.00
Purchase #4	$149.29	11.398%	$166.3061	$166.31	$166.30	$166.30
Purchase #5	$75.82	10.282%	$83.6158	$83.62	$83.60	$83.60
Purchase #6	$56.84	4.308%	$59.2887	$59.29	$59.30	$59.30
Purchase #7	$144.60	5.678%	$152.8104	$152.81	$152.80	$152.80
7 purchase totals =	$681.88		$743.2415	$743.26	$743.25	$743.30