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	$136.66	6.795%	$145.946	$145.95	$145.95	$145.90
Purchase #2	$105.52	3.111%	$108.8027	$108.80	$108.80	$108.80
Purchase #3	$218.92	5.274%	$230.4658	$230.47	$230.45	$230.50
Purchase #4	$217.34	10.712%	$240.6215	$240.62	$240.60	$240.60
Purchase #5	$235.34	7.836%	$253.7812	$253.78	$253.80	$253.80
Purchase #6	$41.67	5.197%	$43.8356	$43.84	$43.85	$43.80
Purchase #7	$128.46	11.208%	$142.8578	$142.86	$142.85	$142.90
7 purchase totals =	$1,083.91		$1,166.3106	$1,166.32	$1,166.30	$1,166.30