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	$225.39	5.758%	$238.368	$238.37	$238.35	$238.40
Purchase #2	$58.43	13.388%	$66.2526	$66.25	$66.25	$66.30
Purchase #3	$51.30	6.601%	$54.6863	$54.69	$54.70	$54.70
Purchase #4	$169.89	13.326%	$192.5295	$192.53	$192.55	$192.50
Purchase #5	$176.81	10.237%	$194.91	$194.91	$194.90	$194.90
Purchase #6	$17.37	8.442%	$18.8364	$18.84	$18.85	$18.80
Purchase #7	$99.31	3.811%	$103.0947	$103.09	$103.10	$103.10
7 purchase totals =	$798.50		$868.6775	$868.68	$868.70	$868.70