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	$96.58	8.739%	$105.0201	$105.02	$105.00	$105.00
Purchase #2	$21.54	5.139%	$22.6469	$22.65	$22.65	$22.60
Purchase #3	$239.52	13.777%	$272.5187	$272.52	$272.50	$272.50
Purchase #4	$97.38	11.567%	$108.6439	$108.64	$108.65	$108.60
Purchase #5	$130.89	9.696%	$143.5811	$143.58	$143.60	$143.60
Purchase #6	$58.48	11.796%	$65.3783	$65.38	$65.40	$65.40
Purchase #7	$79.39	10.624%	$87.8244	$87.82	$87.80	$87.80
7 purchase totals =	$723.78		$805.6134	$805.61	$805.60	$805.50