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	$81.62	3.556%	$84.5224	$84.52	$84.50	$84.50
Purchase #2	$109.50	13.746%	$124.5519	$124.55	$124.55	$124.60
Purchase #3	$52.37	4.334%	$54.6397	$54.64	$54.65	$54.60
Purchase #4	$160.59	10.278%	$177.0954	$177.10	$177.10	$177.10
Purchase #5	$112.59	13.272%	$127.5329	$127.53	$127.55	$127.50
Purchase #6	$203.50	9.128%	$222.0755	$222.08	$222.10	$222.10
Purchase #7	$238.86	4.129%	$248.7225	$248.72	$248.70	$248.70
7 purchase totals =	$959.03		$1,039.1403	$1,039.14	$1,039.15	$1,039.10