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	$114.33	11.423%	$127.3899	$127.39	$127.40	$127.40
Purchase #2	$127.65	3.287%	$131.8459	$131.85	$131.85	$131.80
Purchase #3	$136.95	10.608%	$151.4777	$151.48	$151.50	$151.50
Purchase #4	$128.26	11.406%	$142.8893	$142.89	$142.90	$142.90
Purchase #5	$15.95	9.307%	$17.4345	$17.43	$17.45	$17.40
Purchase #6	$237.58	11.759%	$265.517	$265.52	$265.50	$265.50
Purchase #7	$74.56	12.664%	$84.0023	$84.00	$84.00	$84.00
7 purchase totals =	$835.28		$920.5566	$920.56	$920.60	$920.50