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	$27.47	4.151%	$28.6103	$28.61	$28.60	$28.60
Purchase #2	$192.83	11.843%	$215.6669	$215.67	$215.65	$215.70
Purchase #3	$217.79	12.127%	$244.2014	$244.20	$244.20	$244.20
Purchase #4	$53.55	10.349%	$59.0919	$59.09	$59.10	$59.10
Purchase #5	$203.42	9.223%	$222.1814	$222.18	$222.20	$222.20
Purchase #6	$83.92	13.444%	$95.2022	$95.20	$95.20	$95.20
Purchase #7	$177.70	3.808%	$184.4668	$184.47	$184.45	$184.50
7 purchase totals =	$956.68		$1,049.4209	$1,049.42	$1,049.40	$1,049.50