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	$69.55	4.630%	$72.7702	$72.77	$72.75	$72.80
Purchase #2	$224.95	6.504%	$239.5807	$239.58	$239.60	$239.60
Purchase #3	$61.44	6.694%	$65.5528	$65.55	$65.55	$65.60
Purchase #4	$35.39	8.839%	$38.5181	$38.52	$38.50	$38.50
Purchase #5	$167.86	11.537%	$187.226	$187.23	$187.25	$187.20
Purchase #6	$43.37	11.326%	$48.2821	$48.28	$48.30	$48.30
Purchase #7	$11.71	3.363%	$12.1038	$12.10	$12.10	$12.10
7 purchase totals =	$614.27		$664.0337	$664.03	$664.05	$664.10