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	$145.92	10.242%	$160.8651	$160.87	$160.85	$160.90
Purchase #2	$127.41	12.463%	$143.2891	$143.29	$143.30	$143.30
Purchase #3	$145.67	10.475%	$160.9289	$160.93	$160.95	$160.90
Purchase #4	$81.66	7.429%	$87.7265	$87.73	$87.75	$87.70
Purchase #5	$113.79	11.739%	$127.1478	$127.15	$127.15	$127.10
Purchase #6	$50.84	7.302%	$54.5523	$54.55	$54.55	$54.60
Purchase #7	$240.56	8.514%	$261.0413	$261.04	$261.05	$261.00
7 purchase totals =	$905.85		$995.5510	$995.56	$995.60	$995.50