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	$100.32	11.118%	$111.4736	$111.47	$111.45	$111.50
Purchase #2	$245.36	6.165%	$260.4864	$260.49	$260.50	$260.50
Purchase #3	$15.60	10.553%	$17.2463	$17.25	$17.25	$17.20
Purchase #4	$146.62	3.617%	$151.9232	$151.92	$151.90	$151.90
Purchase #5	$105.47	7.143%	$113.0037	$113.00	$113.00	$113.00
Purchase #6	$95.31	6.504%	$101.509	$101.51	$101.50	$101.50
Purchase #7	$230.97	11.529%	$257.5985	$257.60	$257.60	$257.60
7 purchase totals =	$939.65		$1,013.2407	$1,013.24	$1,013.20	$1,013.20