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	$23.42	10.270%	$25.8252	$25.83	$25.85	$25.80
Purchase #2	$240.65	5.522%	$253.9387	$253.94	$253.95	$253.90
Purchase #3	$237.81	13.325%	$269.4982	$269.50	$269.50	$269.50
Purchase #4	$140.61	10.786%	$155.7762	$155.78	$155.80	$155.80
Purchase #5	$78.52	10.285%	$86.5958	$86.60	$86.60	$86.60
Purchase #6	$177.68	4.298%	$185.3167	$185.32	$185.30	$185.30
Purchase #7	$57.25	8.553%	$62.1466	$62.15	$62.15	$62.10
7 purchase totals =	$955.94		$1,039.0974	$1,039.12	$1,039.15	$1,039.00