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	$69.69	12.527%	$78.4201	$78.42	$78.40	$78.40
Purchase #2	$19.42	11.172%	$21.5896	$21.59	$21.60	$21.60
Purchase #3	$10.92	6.402%	$11.6191	$11.62	$11.60	$11.60
Purchase #4	$54.27	12.110%	$60.8421	$60.84	$60.85	$60.80
Purchase #5	$90.72	10.535%	$100.2774	$100.28	$100.30	$100.30
Purchase #6	$40.99	9.404%	$44.8447	$44.84	$44.85	$44.80
Purchase #7	$198.99	8.706%	$216.3141	$216.31	$216.30	$216.30
7 purchase totals =	$485.00		$533.9071	$533.90	$533.90	$533.80