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	$65.32	13.689%	$74.2617	$74.26	$74.25	$74.30
Purchase #2	$24.42	13.843%	$27.8005	$27.80	$27.80	$27.80
Purchase #3	$131.77	9.786%	$144.665	$144.67	$144.65	$144.70
Purchase #4	$140.25	13.277%	$158.871	$158.87	$158.85	$158.90
Purchase #5	$29.75	13.785%	$33.851	$33.85	$33.85	$33.90
Purchase #6	$24.71	13.509%	$28.0481	$28.05	$28.05	$28.00
Purchase #7	$62.71	7.558%	$67.4496	$67.45	$67.45	$67.40
7 purchase totals =	$478.93		$534.9469	$534.95	$534.90	$535.00