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	$107.58	8.379%	$116.5941	$116.59	$116.60	$116.60
Purchase #2	$225.83	5.624%	$238.5307	$238.53	$238.55	$238.50
Purchase #3	$184.38	11.716%	$205.982	$205.98	$206.00	$206.00
Purchase #4	$222.25	7.200%	$238.252	$238.25	$238.25	$238.30
Purchase #5	$249.59	6.715%	$266.35	$266.35	$266.35	$266.40
Purchase #6	$195.42	6.857%	$208.8199	$208.82	$208.80	$208.80
Purchase #7	$229.51	11.405%	$255.6856	$255.69	$255.70	$255.70
7 purchase totals =	$1,414.56		$1,530.2143	$1,530.21	$1,530.25	$1,530.30