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	$61.92	10.700%	$68.5454	$68.55	$68.55	$68.50
Purchase #2	$40.77	7.381%	$43.7792	$43.78	$43.80	$43.80
Purchase #3	$132.51	8.108%	$143.2539	$143.25	$143.25	$143.30
Purchase #4	$246.82	6.482%	$262.8189	$262.82	$262.80	$262.80
Purchase #5	$177.69	5.475%	$187.4185	$187.42	$187.40	$187.40
Purchase #6	$57.48	9.262%	$62.8038	$62.80	$62.80	$62.80
Purchase #7	$118.26	7.855%	$127.5493	$127.55	$127.55	$127.50
7 purchase totals =	$835.45		$896.1690	$896.17	$896.15	$896.10