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	$56.51	12.577%	$63.6173	$63.62	$63.60	$63.60
Purchase #2	$237.62	5.548%	$250.8032	$250.80	$250.80	$250.80
Purchase #3	$233.38	12.202%	$261.857	$261.86	$261.85	$261.90
Purchase #4	$115.25	13.743%	$131.0888	$131.09	$131.10	$131.10
Purchase #5	$24.71	3.501%	$25.5751	$25.58	$25.60	$25.60
Purchase #6	$133.92	6.403%	$142.4949	$142.49	$142.50	$142.50
Purchase #7	$189.94	3.418%	$196.4321	$196.43	$196.45	$196.40
7 purchase totals =	$991.33		$1,071.8684	$1,071.87	$1,071.90	$1,071.90