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	$133.78	6.357%	$142.2844	$142.28	$142.30	$142.30
Purchase #2	$190.30	5.325%	$200.4335	$200.43	$200.45	$200.40
Purchase #3	$160.38	10.219%	$176.7692	$176.77	$176.75	$176.80
Purchase #4	$134.31	4.630%	$140.5286	$140.53	$140.55	$140.50
Purchase #5	$196.82	10.260%	$217.0137	$217.01	$217.00	$217.00
Purchase #6	$77.77	10.863%	$86.2182	$86.22	$86.20	$86.20
Purchase #7	$65.92	6.400%	$70.1389	$70.14	$70.15	$70.10
7 purchase totals =	$959.28		$1,033.3865	$1,033.38	$1,033.40	$1,033.30