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	$240.38	7.402%	$258.1729	$258.17	$258.15	$258.20
Purchase #2	$194.77	9.559%	$213.3881	$213.39	$213.40	$213.40
Purchase #3	$46.80	4.508%	$48.9097	$48.91	$48.90	$48.90
Purchase #4	$147.50	9.555%	$161.5936	$161.59	$161.60	$161.60
Purchase #5	$200.36	9.104%	$218.6008	$218.60	$218.60	$218.60
Purchase #6	$241.94	10.724%	$267.8856	$267.89	$267.90	$267.90
Purchase #7	$25.58	8.554%	$27.7681	$27.77	$27.75	$27.80
7 purchase totals =	$1,097.33		$1,196.3188	$1,196.32	$1,196.30	$1,196.40