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	$102.86	13.603%	$116.852	$116.85	$116.85	$116.90
Purchase #2	$54.39	9.203%	$59.3955	$59.40	$59.40	$59.40
Purchase #3	$237.82	4.285%	$248.0106	$248.01	$248.00	$248.00
Purchase #4	$117.41	12.549%	$132.1438	$132.14	$132.15	$132.10
Purchase #5	$150.26	5.452%	$158.4522	$158.45	$158.45	$158.50
Purchase #6	$130.52	10.606%	$144.363	$144.36	$144.35	$144.40
Purchase #7	$87.76	12.144%	$98.4176	$98.42	$98.40	$98.40
7 purchase totals =	$881.02		$957.6347	$957.63	$957.60	$957.70