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	$66.54	3.695%	$68.9987	$69.00	$69.00	$69.00
Purchase #2	$191.70	11.625%	$213.9851	$213.99	$214.00	$214.00
Purchase #3	$39.61	13.262%	$44.8631	$44.86	$44.85	$44.90
Purchase #4	$97.25	8.279%	$105.3013	$105.30	$105.30	$105.30
Purchase #5	$158.58	12.324%	$178.1234	$178.12	$178.10	$178.10
Purchase #6	$42.33	3.467%	$43.7976	$43.80	$43.80	$43.80
Purchase #7	$11.62	7.110%	$12.4462	$12.45	$12.45	$12.40
7 purchase totals =	$607.63		$667.5154	$667.52	$667.50	$667.50