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	$217.25	4.585%	$227.2109	$227.21	$227.20	$227.20
Purchase #2	$107.94	8.754%	$117.3891	$117.39	$117.40	$117.40
Purchase #3	$212.60	13.469%	$241.2351	$241.24	$241.25	$241.20
Purchase #4	$229.33	10.568%	$253.5656	$253.57	$253.55	$253.60
Purchase #5	$6.92	10.164%	$7.6233	$7.62	$7.60	$7.60
Purchase #6	$82.86	9.727%	$90.9198	$90.92	$90.90	$90.90
Purchase #7	$208.99	10.325%	$230.5682	$230.57	$230.55	$230.60
7 purchase totals =	$1,065.89		$1,168.5120	$1,168.52	$1,168.45	$1,168.50