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	$167.55	5.207%	$176.2743	$176.27	$176.25	$176.30
Purchase #2	$126.60	5.380%	$133.4111	$133.41	$133.40	$133.40
Purchase #3	$93.46	7.549%	$100.5153	$100.52	$100.50	$100.50
Purchase #4	$182.79	9.660%	$200.4475	$200.45	$200.45	$200.40
Purchase #5	$11.30	6.468%	$12.0309	$12.03	$12.05	$12.00
Purchase #6	$54.88	13.395%	$62.2312	$62.23	$62.25	$62.20
Purchase #7	$180.94	8.590%	$196.4827	$196.48	$196.50	$196.50
7 purchase totals =	$817.52		$881.3930	$881.39	$881.40	$881.30