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	$140.36	9.841%	$154.1728	$154.17	$154.15	$154.20
Purchase #2	$207.90	4.739%	$217.7524	$217.75	$217.75	$217.80
Purchase #3	$54.49	8.552%	$59.15	$59.15	$59.15	$59.20
Purchase #4	$151.97	12.630%	$171.1638	$171.16	$171.15	$171.20
Purchase #5	$34.29	3.631%	$35.5351	$35.54	$35.55	$35.50
Purchase #6	$112.25	3.815%	$116.5323	$116.53	$116.55	$116.50
Purchase #7	$188.78	8.758%	$205.3134	$205.31	$205.30	$205.30
7 purchase totals =	$890.04		$959.6198	$959.61	$959.60	$959.70