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	$36.63	10.562%	$40.4989	$40.50	$40.50	$40.50
Purchase #2	$92.91	8.571%	$100.8733	$100.87	$100.85	$100.90
Purchase #3	$111.29	5.598%	$117.52	$117.52	$117.50	$117.50
Purchase #4	$31.59	10.840%	$35.0144	$35.01	$35.00	$35.00
Purchase #5	$190.25	11.286%	$211.7216	$211.72	$211.70	$211.70
Purchase #6	$130.78	9.660%	$143.4133	$143.41	$143.40	$143.40
Purchase #7	$42.38	10.354%	$46.768	$46.77	$46.75	$46.80
7 purchase totals =	$635.83		$695.8095	$695.80	$695.70	$695.80