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	$61.80	12.697%	$69.6467	$69.65	$69.65	$69.60
Purchase #2	$199.82	6.641%	$213.09	$213.09	$213.10	$213.10
Purchase #3	$249.68	13.761%	$284.0385	$284.04	$284.05	$284.00
Purchase #4	$84.28	7.510%	$90.6094	$90.61	$90.60	$90.60
Purchase #5	$47.78	10.608%	$52.8485	$52.85	$52.85	$52.80
Purchase #6	$38.92	11.747%	$43.4919	$43.49	$43.50	$43.50
Purchase #7	$248.38	12.679%	$279.8721	$279.87	$279.85	$279.90
7 purchase totals =	$930.66		$1,033.5971	$1,033.60	$1,033.60	$1,033.50