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	$248.48	11.313%	$276.5905	$276.59	$276.60	$276.60
Purchase #2	$62.39	5.753%	$65.9793	$65.98	$66.00	$66.00
Purchase #3	$32.85	6.358%	$34.9386	$34.94	$34.95	$34.90
Purchase #4	$172.40	6.483%	$183.5767	$183.58	$183.60	$183.60
Purchase #5	$199.62	3.157%	$205.922	$205.92	$205.90	$205.90
Purchase #6	$139.57	6.705%	$148.9282	$148.93	$148.95	$148.90
Purchase #7	$82.52	3.185%	$85.1483	$85.15	$85.15	$85.10
7 purchase totals =	$937.83		$1,001.0836	$1,001.09	$1,001.15	$1,001.00