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	$85.27	6.265%	$90.6122	$90.61	$90.60	$90.60
Purchase #2	$182.45	9.764%	$200.2644	$200.26	$200.25	$200.30
Purchase #3	$209.40	5.128%	$220.138	$220.14	$220.15	$220.10
Purchase #4	$192.84	8.249%	$208.7474	$208.75	$208.75	$208.70
Purchase #5	$25.52	6.823%	$27.2612	$27.26	$27.25	$27.30
Purchase #6	$111.48	5.789%	$117.9336	$117.93	$117.95	$117.90
Purchase #7	$191.43	12.749%	$215.8354	$215.84	$215.85	$215.80
7 purchase totals =	$998.39		$1,080.7922	$1,080.79	$1,080.80	$1,080.70