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	$218.75	10.600%	$241.9375	$241.94	$241.95	$241.90
Purchase #2	$95.58	5.103%	$100.4574	$100.46	$100.45	$100.50
Purchase #3	$79.25	12.509%	$89.1634	$89.16	$89.15	$89.20
Purchase #4	$141.71	3.428%	$146.5678	$146.57	$146.55	$146.60
Purchase #5	$232.89	12.567%	$262.1573	$262.16	$262.15	$262.20
Purchase #6	$176.34	9.130%	$192.4398	$192.44	$192.45	$192.40
Purchase #7	$227.87	6.558%	$242.8137	$242.81	$242.80	$242.80
7 purchase totals =	$1,172.39		$1,275.5369	$1,275.54	$1,275.50	$1,275.60