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	$62.66	10.230%	$69.0701	$69.07	$69.05	$69.10
Purchase #2	$116.39	9.264%	$127.1724	$127.17	$127.15	$127.20
Purchase #3	$131.80	13.831%	$150.0293	$150.03	$150.05	$150.00
Purchase #4	$9.38	12.165%	$10.5211	$10.52	$10.50	$10.50
Purchase #5	$29.30	7.286%	$31.4348	$31.43	$31.45	$31.40
Purchase #6	$87.49	10.392%	$96.582	$96.58	$96.60	$96.60
Purchase #7	$158.98	13.139%	$179.8684	$179.87	$179.85	$179.90
7 purchase totals =	$596.00		$664.6781	$664.67	$664.65	$664.70