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	$161.42	6.457%	$171.8429	$171.84	$171.85	$171.80
Purchase #2	$180.67	8.817%	$196.5997	$196.60	$196.60	$196.60
Purchase #3	$230.78	9.602%	$252.9395	$252.94	$252.95	$252.90
Purchase #4	$127.55	12.457%	$143.4389	$143.44	$143.45	$143.40
Purchase #5	$13.67	8.469%	$14.8277	$14.83	$14.85	$14.80
Purchase #6	$92.39	3.661%	$95.7724	$95.77	$95.75	$95.80
Purchase #7	$133.95	7.808%	$144.4088	$144.41	$144.40	$144.40
7 purchase totals =	$940.43		$1,019.8299	$1,019.83	$1,019.85	$1,019.70