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	$12.92	5.612%	$13.6451	$13.65	$13.65	$13.60
Purchase #2	$185.82	7.633%	$200.0036	$200.00	$200.00	$200.00
Purchase #3	$45.46	8.128%	$49.155	$49.16	$49.15	$49.20
Purchase #4	$41.97	10.628%	$46.4306	$46.43	$46.45	$46.40
Purchase #5	$246.83	3.670%	$255.8887	$255.89	$255.90	$255.90
Purchase #6	$9.38	11.604%	$10.4685	$10.47	$10.45	$10.50
Purchase #7	$177.78	6.776%	$189.8264	$189.83	$189.85	$189.80
7 purchase totals =	$720.16		$765.4179	$765.43	$765.45	$765.40