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	$119.30	7.444%	$128.1807	$128.18	$128.20	$128.20
Purchase #2	$69.39	7.861%	$74.8447	$74.84	$74.85	$74.80
Purchase #3	$92.87	8.260%	$100.5411	$100.54	$100.55	$100.50
Purchase #4	$86.30	13.844%	$98.2474	$98.25	$98.25	$98.20
Purchase #5	$208.97	10.337%	$230.5712	$230.57	$230.55	$230.60
Purchase #6	$154.37	11.120%	$171.5359	$171.54	$171.55	$171.50
Purchase #7	$17.72	4.127%	$18.4513	$18.45	$18.45	$18.50
7 purchase totals =	$748.92		$822.3723	$822.37	$822.40	$822.30