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	$132.54	8.325%	$143.574	$143.57	$143.55	$143.60
Purchase #2	$63.32	6.587%	$67.4909	$67.49	$67.50	$67.50
Purchase #3	$87.82	5.828%	$92.9381	$92.94	$92.95	$92.90
Purchase #4	$124.41	3.803%	$129.1413	$129.14	$129.15	$129.10
Purchase #5	$49.88	6.343%	$53.0439	$53.04	$53.05	$53.00
Purchase #6	$42.44	7.432%	$45.5941	$45.59	$45.60	$45.60
Purchase #7	$140.60	6.717%	$150.0441	$150.04	$150.05	$150.00
7 purchase totals =	$641.01		$681.8264	$681.81	$681.85	$681.70