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	$54.60	9.553%	$59.8159	$59.82	$59.80	$59.80
Purchase #2	$24.76	6.108%	$26.2723	$26.27	$26.25	$26.30
Purchase #3	$127.52	13.644%	$144.9188	$144.92	$144.90	$144.90
Purchase #4	$179.90	4.163%	$187.3892	$187.39	$187.40	$187.40
Purchase #5	$160.44	6.861%	$171.4478	$171.45	$171.45	$171.40
Purchase #6	$222.38	5.739%	$235.1424	$235.14	$235.15	$235.10
Purchase #7	$128.48	4.814%	$134.665	$134.67	$134.65	$134.70
7 purchase totals =	$898.08		$959.6514	$959.66	$959.60	$959.60