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	$136.66	7.118%	$146.3875	$146.39	$146.40	$146.40
Purchase #2	$116.45	6.627%	$124.1671	$124.17	$124.15	$124.20
Purchase #3	$98.47	10.565%	$108.8734	$108.87	$108.85	$108.90
Purchase #4	$143.54	8.574%	$155.8471	$155.85	$155.85	$155.80
Purchase #5	$213.28	9.287%	$233.0873	$233.09	$233.10	$233.10
Purchase #6	$118.90	11.426%	$132.4855	$132.49	$132.50	$132.50
Purchase #7	$228.27	5.838%	$241.5964	$241.60	$241.60	$241.60
7 purchase totals =	$1,055.57		$1,142.4443	$1,142.46	$1,142.45	$1,142.50