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	$212.37	4.827%	$222.6211	$222.62	$222.60	$222.60
Purchase #2	$63.49	10.509%	$70.1622	$70.16	$70.15	$70.20
Purchase #3	$62.39	3.397%	$64.5094	$64.51	$64.50	$64.50
Purchase #4	$34.51	7.410%	$37.0672	$37.07	$37.05	$37.10
Purchase #5	$18.53	4.722%	$19.405	$19.41	$19.40	$19.40
Purchase #6	$81.74	9.325%	$89.3623	$89.36	$89.35	$89.40
Purchase #7	$9.89	8.648%	$10.7453	$10.75	$10.75	$10.70
7 purchase totals =	$482.92		$513.8725	$513.88	$513.80	$513.90