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	$19.42	6.442%	$20.671	$20.67	$20.65	$20.70
Purchase #2	$63.78	5.236%	$67.1195	$67.12	$67.10	$67.10
Purchase #3	$208.94	11.613%	$233.2042	$233.20	$233.20	$233.20
Purchase #4	$69.54	5.864%	$73.6178	$73.62	$73.60	$73.60
Purchase #5	$128.64	3.307%	$132.8941	$132.89	$132.90	$132.90
Purchase #6	$92.42	5.368%	$97.3811	$97.38	$97.40	$97.40
Purchase #7	$116.90	12.280%	$131.2553	$131.26	$131.25	$131.30
7 purchase totals =	$699.64		$756.1430	$756.14	$756.10	$756.20