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	$104.84	6.339%	$111.4858	$111.49	$111.50	$111.50
Purchase #2	$213.58	7.387%	$229.3572	$229.36	$229.35	$229.40
Purchase #3	$148.70	13.280%	$168.4474	$168.45	$168.45	$168.40
Purchase #4	$59.99	9.636%	$65.7706	$65.77	$65.75	$65.80
Purchase #5	$116.29	3.618%	$120.4974	$120.50	$120.50	$120.50
Purchase #6	$195.69	5.587%	$206.6232	$206.62	$206.60	$206.60
Purchase #7	$199.84	10.680%	$221.1829	$221.18	$221.20	$221.20
7 purchase totals =	$1,038.93		$1,123.3645	$1,123.37	$1,123.35	$1,123.40