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	$132.53	9.803%	$145.5219	$145.52	$145.50	$145.50
Purchase #2	$148.41	6.472%	$158.0151	$158.02	$158.00	$158.00
Purchase #3	$67.99	13.488%	$77.1605	$77.16	$77.15	$77.20
Purchase #4	$118.75	4.238%	$123.7826	$123.78	$123.80	$123.80
Purchase #5	$58.56	13.505%	$66.4685	$66.47	$66.45	$66.50
Purchase #6	$95.72	8.785%	$104.129	$104.13	$104.15	$104.10
Purchase #7	$220.91	9.509%	$241.9163	$241.92	$241.90	$241.90
7 purchase totals =	$842.87		$916.9939	$917.00	$916.95	$917.00