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	$216.43	12.636%	$243.7781	$243.78	$243.80	$243.80
Purchase #2	$129.52	11.768%	$144.7619	$144.76	$144.75	$144.80
Purchase #3	$41.56	7.851%	$44.8229	$44.82	$44.80	$44.80
Purchase #4	$244.41	6.208%	$259.583	$259.58	$259.60	$259.60
Purchase #5	$241.49	12.822%	$272.4538	$272.45	$272.45	$272.50
Purchase #6	$155.49	3.451%	$160.856	$160.86	$160.85	$160.90
Purchase #7	$38.78	10.262%	$42.7596	$42.76	$42.75	$42.80
7 purchase totals =	$1,067.68		$1,169.0153	$1,169.01	$1,169.00	$1,169.20