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	$250.53	12.599%	$282.0943	$282.09	$282.10	$282.10
Purchase #2	$78.60	3.588%	$81.4202	$81.42	$81.40	$81.40
Purchase #3	$107.72	4.814%	$112.9056	$112.91	$112.90	$112.90
Purchase #4	$138.50	3.262%	$143.0179	$143.02	$143.00	$143.00
Purchase #5	$120.38	9.557%	$131.8847	$131.88	$131.90	$131.90
Purchase #6	$119.78	9.548%	$131.2166	$131.22	$131.20	$131.20
Purchase #7	$170.57	8.775%	$185.5375	$185.54	$185.55	$185.50
7 purchase totals =	$986.08		$1,068.0768	$1,068.08	$1,068.05	$1,068.00