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	$13.56	6.664%	$14.4636	$14.46	$14.45	$14.50
Purchase #2	$30.66	9.523%	$33.5798	$33.58	$33.60	$33.60
Purchase #3	$9.32	13.405%	$10.5693	$10.57	$10.55	$10.60
Purchase #4	$239.69	10.810%	$265.6005	$265.60	$265.60	$265.60
Purchase #5	$165.80	11.312%	$184.5553	$184.56	$184.55	$184.60
Purchase #6	$34.69	10.685%	$38.3966	$38.40	$38.40	$38.40
Purchase #7	$216.54	10.638%	$239.5755	$239.58	$239.60	$239.60
7 purchase totals =	$710.26		$786.7406	$786.75	$786.75	$786.90