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	$119.86	3.310%	$123.8274	$123.83	$123.85	$123.80
Purchase #2	$65.31	8.284%	$70.7203	$70.72	$70.70	$70.70
Purchase #3	$19.60	8.462%	$21.2586	$21.26	$21.25	$21.30
Purchase #4	$235.88	10.237%	$260.027	$260.03	$260.05	$260.00
Purchase #5	$105.26	10.684%	$116.506	$116.51	$116.50	$116.50
Purchase #6	$239.59	11.789%	$267.8353	$267.84	$267.85	$267.80
Purchase #7	$179.64	9.353%	$196.4417	$196.44	$196.45	$196.40
7 purchase totals =	$965.14		$1,056.6163	$1,056.63	$1,056.65	$1,056.50