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	$171.44	11.739%	$191.5653	$191.57	$191.55	$191.60
Purchase #2	$208.49	6.751%	$222.5652	$222.57	$222.55	$222.60
Purchase #3	$67.87	6.730%	$72.4377	$72.44	$72.45	$72.40
Purchase #4	$76.30	13.724%	$86.7714	$86.77	$86.75	$86.80
Purchase #5	$8.72	3.527%	$9.0276	$9.03	$9.05	$9.00
Purchase #6	$52.51	4.461%	$54.8525	$54.85	$54.85	$54.90
Purchase #7	$112.61	13.331%	$127.622	$127.62	$127.60	$127.60
7 purchase totals =	$697.94		$764.8417	$764.85	$764.80	$764.90