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	$197.91	11.109%	$219.8958	$219.90	$219.90	$219.90
Purchase #2	$40.91	12.492%	$46.0205	$46.02	$46.00	$46.00
Purchase #3	$150.80	5.768%	$159.4981	$159.50	$159.50	$159.50
Purchase #4	$219.79	5.231%	$231.2872	$231.29	$231.30	$231.30
Purchase #5	$207.40	11.333%	$230.9046	$230.90	$230.90	$230.90
Purchase #6	$21.69	7.861%	$23.3951	$23.40	$23.40	$23.40
Purchase #7	$240.44	6.218%	$255.3906	$255.39	$255.40	$255.40
7 purchase totals =	$1,078.94		$1,166.3919	$1,166.40	$1,166.40	$1,166.40