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	$240.50	6.201%	$255.4134	$255.41	$255.40	$255.40
Purchase #2	$30.86	12.786%	$34.8058	$34.81	$34.80	$34.80
Purchase #3	$75.75	4.149%	$78.8929	$78.89	$78.90	$78.90
Purchase #4	$179.53	5.206%	$188.8763	$188.88	$188.90	$188.90
Purchase #5	$64.25	3.115%	$66.2514	$66.25	$66.25	$66.30
Purchase #6	$238.62	7.504%	$256.526	$256.53	$256.55	$256.50
Purchase #7	$137.99	5.518%	$145.6043	$145.60	$145.60	$145.60
7 purchase totals =	$967.50		$1,026.3701	$1,026.37	$1,026.40	$1,026.40