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	$11.90	6.866%	$12.7171	$12.72	$12.70	$12.70
Purchase #2	$198.49	10.766%	$219.8594	$219.86	$219.85	$219.90
Purchase #3	$88.56	9.196%	$96.704	$96.70	$96.70	$96.70
Purchase #4	$143.95	10.382%	$158.8949	$158.89	$158.90	$158.90
Purchase #5	$182.32	4.397%	$190.3366	$190.34	$190.35	$190.30
Purchase #6	$135.78	6.721%	$144.9058	$144.91	$144.90	$144.90
Purchase #7	$172.75	11.348%	$192.3537	$192.35	$192.35	$192.40
7 purchase totals =	$933.75		$1,015.7715	$1,015.77	$1,015.75	$1,015.80