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	$10.67	7.172%	$11.4353	$11.44	$11.45	$11.40
Purchase #2	$171.46	11.741%	$191.5911	$191.59	$191.60	$191.60
Purchase #3	$10.70	4.704%	$11.2033	$11.20	$11.20	$11.20
Purchase #4	$140.43	7.171%	$150.5002	$150.50	$150.50	$150.50
Purchase #5	$196.30	13.190%	$222.192	$222.19	$222.20	$222.20
Purchase #6	$230.47	6.256%	$244.8882	$244.89	$244.90	$244.90
Purchase #7	$34.26	8.471%	$37.1622	$37.16	$37.15	$37.20
7 purchase totals =	$794.29		$868.9723	$868.97	$869.00	$869.00