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	$36.78	5.525%	$38.8121	$38.81	$38.80	$38.80
Purchase #2	$59.32	5.556%	$62.6158	$62.62	$62.60	$62.60
Purchase #3	$60.65	3.657%	$62.868	$62.87	$62.85	$62.90
Purchase #4	$43.36	12.283%	$48.6859	$48.69	$48.70	$48.70
Purchase #5	$158.94	3.340%	$164.2486	$164.25	$164.25	$164.20
Purchase #6	$105.41	12.705%	$118.8023	$118.80	$118.80	$118.80
Purchase #7	$176.47	7.853%	$190.3282	$190.33	$190.35	$190.30
7 purchase totals =	$640.93		$686.3609	$686.37	$686.35	$686.30