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	$149.62	6.633%	$159.5443	$159.54	$159.55	$159.50
Purchase #2	$152.45	5.800%	$161.2921	$161.29	$161.30	$161.30
Purchase #3	$49.32	13.564%	$56.0098	$56.01	$56.00	$56.00
Purchase #4	$59.73	10.684%	$66.1116	$66.11	$66.10	$66.10
Purchase #5	$218.60	13.641%	$248.4192	$248.42	$248.40	$248.40
Purchase #6	$175.28	7.192%	$187.8861	$187.89	$187.90	$187.90
Purchase #7	$124.59	11.675%	$139.1359	$139.14	$139.15	$139.10
7 purchase totals =	$929.59		$1,018.3990	$1,018.40	$1,018.40	$1,018.30