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	$13.59	4.287%	$14.1726	$14.17	$14.15	$14.20
Purchase #2	$60.38	11.412%	$67.2706	$67.27	$67.25	$67.30
Purchase #3	$153.69	9.682%	$168.5703	$168.57	$168.55	$168.60
Purchase #4	$240.30	13.164%	$271.9331	$271.93	$271.95	$271.90
Purchase #5	$90.37	10.773%	$100.1056	$100.11	$100.10	$100.10
Purchase #6	$207.55	5.856%	$219.7041	$219.70	$219.70	$219.70
Purchase #7	$115.55	9.566%	$126.6035	$126.60	$126.60	$126.60
7 purchase totals =	$881.43		$968.3598	$968.35	$968.30	$968.40