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	$10.59	5.472%	$11.1695	$11.17	$11.15	$11.20
Purchase #2	$40.40	13.106%	$45.6948	$45.69	$45.70	$45.70
Purchase #3	$96.58	4.436%	$100.8643	$100.86	$100.85	$100.90
Purchase #4	$242.28	12.540%	$272.6619	$272.66	$272.65	$272.70
Purchase #5	$245.57	8.135%	$265.5471	$265.55	$265.55	$265.50
Purchase #6	$211.61	10.308%	$233.4228	$233.42	$233.40	$233.40
Purchase #7	$35.34	10.445%	$39.0313	$39.03	$39.05	$39.00
7 purchase totals =	$882.37		$968.3917	$968.38	$968.35	$968.40