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	$128.86	11.190%	$143.2794	$143.28	$143.30	$143.30
Purchase #2	$224.55	6.352%	$238.8134	$238.81	$238.80	$238.80
Purchase #3	$198.94	10.637%	$220.1012	$220.10	$220.10	$220.10
Purchase #4	$118.79	5.146%	$124.9029	$124.90	$124.90	$124.90
Purchase #5	$163.96	4.603%	$171.5071	$171.51	$171.50	$171.50
Purchase #6	$122.85	3.614%	$127.2898	$127.29	$127.30	$127.30
Purchase #7	$108.27	7.556%	$116.4509	$116.45	$116.45	$116.50
7 purchase totals =	$1,066.22		$1,142.3447	$1,142.34	$1,142.35	$1,142.40