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	$109.39	6.545%	$116.5496	$116.55	$116.55	$116.50
Purchase #2	$61.95	6.511%	$65.9836	$65.98	$66.00	$66.00
Purchase #3	$200.39	8.752%	$217.9281	$217.93	$217.95	$217.90
Purchase #4	$248.95	5.399%	$262.3908	$262.39	$262.40	$262.40
Purchase #5	$139.41	3.673%	$144.5305	$144.53	$144.55	$144.50
Purchase #6	$199.89	7.149%	$214.1801	$214.18	$214.20	$214.20
Purchase #7	$58.63	11.406%	$65.3173	$65.32	$65.30	$65.30
7 purchase totals =	$1,018.61		$1,086.8800	$1,086.88	$1,086.95	$1,086.80