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	$103.38	10.291%	$114.0188	$114.02	$114.00	$114.00
Purchase #2	$176.60	3.763%	$183.2455	$183.25	$183.25	$183.20
Purchase #3	$151.57	13.801%	$172.4882	$172.49	$172.50	$172.50
Purchase #4	$132.44	11.389%	$147.5236	$147.52	$147.50	$147.50
Purchase #5	$37.80	13.161%	$42.7749	$42.77	$42.75	$42.80
Purchase #6	$220.83	12.676%	$248.8224	$248.82	$248.80	$248.80
Purchase #7	$62.90	11.115%	$69.8913	$69.89	$69.90	$69.90
7 purchase totals =	$885.52		$978.7647	$978.76	$978.70	$978.70