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	$82.38	8.688%	$89.5372	$89.54	$89.55	$89.50
Purchase #2	$53.74	4.377%	$56.0922	$56.09	$56.10	$56.10
Purchase #3	$139.95	13.547%	$158.909	$158.91	$158.90	$158.90
Purchase #4	$155.70	13.406%	$176.5731	$176.57	$176.55	$176.60
Purchase #5	$210.81	7.642%	$226.9201	$226.92	$226.90	$226.90
Purchase #6	$217.59	12.156%	$244.0402	$244.04	$244.05	$244.00
Purchase #7	$73.39	11.604%	$81.9062	$81.91	$81.90	$81.90
7 purchase totals =	$933.56		$1,033.9780	$1,033.98	$1,033.95	$1,033.90