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	$43.56	8.561%	$47.2892	$47.29	$47.30	$47.30
Purchase #2	$248.94	3.255%	$257.043	$257.04	$257.05	$257.00
Purchase #3	$53.60	11.516%	$59.7726	$59.77	$59.75	$59.80
Purchase #4	$127.64	12.384%	$143.4469	$143.45	$143.45	$143.40
Purchase #5	$197.47	11.491%	$220.1613	$220.16	$220.15	$220.20
Purchase #6	$51.58	5.254%	$54.29	$54.29	$54.30	$54.30
Purchase #7	$143.95	11.545%	$160.569	$160.57	$160.55	$160.60
7 purchase totals =	$866.74		$942.5720	$942.57	$942.55	$942.60