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	$132.48	10.103%	$145.8645	$145.86	$145.85	$145.90
Purchase #2	$123.53	11.572%	$137.8249	$137.82	$137.80	$137.80
Purchase #3	$93.48	6.460%	$99.5188	$99.52	$99.50	$99.50
Purchase #4	$131.48	4.657%	$137.603	$137.60	$137.60	$137.60
Purchase #5	$60.65	8.800%	$65.9872	$65.99	$66.00	$66.00
Purchase #6	$103.56	10.155%	$114.0765	$114.08	$114.10	$114.10
Purchase #7	$137.46	3.651%	$142.4787	$142.48	$142.50	$142.50
7 purchase totals =	$782.64		$843.3536	$843.35	$843.35	$843.40