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	$42.43	5.594%	$44.8035	$44.80	$44.80	$44.80
Purchase #2	$143.49	5.805%	$151.8196	$151.82	$151.80	$151.80
Purchase #3	$11.94	3.140%	$12.3149	$12.31	$12.30	$12.30
Purchase #4	$27.83	3.553%	$28.8188	$28.82	$28.80	$28.80
Purchase #5	$238.32	13.114%	$269.5733	$269.57	$269.55	$269.60
Purchase #6	$190.64	9.299%	$208.3676	$208.37	$208.35	$208.40
Purchase #7	$213.73	5.314%	$225.0876	$225.09	$225.10	$225.10
7 purchase totals =	$868.38		$940.7853	$940.78	$940.70	$940.80