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	$33.32	8.830%	$36.2622	$36.26	$36.25	$36.30
Purchase #2	$158.30	9.627%	$173.5395	$173.54	$173.55	$173.50
Purchase #3	$22.55	8.475%	$24.4611	$24.46	$24.45	$24.50
Purchase #4	$134.75	5.477%	$142.1303	$142.13	$142.15	$142.10
Purchase #5	$112.82	7.783%	$121.6008	$121.60	$121.60	$121.60
Purchase #6	$78.56	11.660%	$87.7201	$87.72	$87.70	$87.70
Purchase #7	$181.31	10.569%	$200.4727	$200.47	$200.45	$200.50
7 purchase totals =	$721.61		$786.1867	$786.18	$786.15	$786.20