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	$40.30	3.759%	$41.8149	$41.81	$41.80	$41.80
Purchase #2	$94.64	9.379%	$103.5163	$103.52	$103.50	$103.50
Purchase #3	$250.62	7.865%	$270.3313	$270.33	$270.35	$270.30
Purchase #4	$227.49	7.293%	$244.0808	$244.08	$244.10	$244.10
Purchase #5	$224.37	4.184%	$233.7576	$233.76	$233.75	$233.80
Purchase #6	$102.89	8.493%	$111.6284	$111.63	$111.65	$111.60
Purchase #7	$8.54	10.397%	$9.4279	$9.43	$9.45	$9.40
7 purchase totals =	$948.85		$1,014.5572	$1,014.56	$1,014.60	$1,014.50