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	$57.66	5.836%	$61.025	$61.03	$61.05	$61.00
Purchase #2	$45.94	8.724%	$49.9478	$49.95	$49.95	$49.90
Purchase #3	$163.86	5.390%	$172.6921	$172.69	$172.70	$172.70
Purchase #4	$69.72	9.730%	$76.5038	$76.50	$76.50	$76.50
Purchase #5	$110.84	6.870%	$118.4547	$118.45	$118.45	$118.50
Purchase #6	$17.68	11.719%	$19.7519	$19.75	$19.75	$19.80
Purchase #7	$156.28	8.400%	$169.4075	$169.41	$169.40	$169.40
7 purchase totals =	$621.98		$667.7828	$667.78	$667.80	$667.80