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	$176.74	6.751%	$188.6717	$188.67	$188.65	$188.70
Purchase #2	$41.52	9.617%	$45.513	$45.51	$45.50	$45.50
Purchase #3	$175.59	7.174%	$188.1868	$188.19	$188.20	$188.20
Purchase #4	$201.97	11.693%	$225.5864	$225.59	$225.60	$225.60
Purchase #5	$238.47	7.212%	$255.6685	$255.67	$255.65	$255.70
Purchase #6	$75.62	13.461%	$85.7992	$85.80	$85.80	$85.80
Purchase #7	$103.97	7.748%	$112.0256	$112.03	$112.05	$112.00
7 purchase totals =	$1,013.88		$1,101.4512	$1,101.46	$1,101.45	$1,101.50