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	$14.42	8.656%	$15.6682	$15.67	$15.65	$15.70
Purchase #2	$175.60	13.709%	$199.673	$199.67	$199.65	$199.70
Purchase #3	$130.31	3.362%	$134.691	$134.69	$134.70	$134.70
Purchase #4	$6.31	3.608%	$6.5377	$6.54	$6.55	$6.50
Purchase #5	$241.76	6.422%	$257.2858	$257.29	$257.30	$257.30
Purchase #6	$38.42	10.429%	$42.4268	$42.43	$42.45	$42.40
Purchase #7	$86.31	3.762%	$89.557	$89.56	$89.55	$89.60
7 purchase totals =	$693.13		$745.8395	$745.85	$745.85	$745.90