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	$106.62	4.508%	$111.4264	$111.43	$111.45	$111.40
Purchase #2	$131.45	10.203%	$144.8618	$144.86	$144.85	$144.90
Purchase #3	$75.32	10.861%	$83.5005	$83.50	$83.50	$83.50
Purchase #4	$222.35	4.509%	$232.3758	$232.38	$232.40	$232.40
Purchase #5	$78.37	6.614%	$83.5534	$83.55	$83.55	$83.60
Purchase #6	$217.92	3.282%	$225.0721	$225.07	$225.05	$225.10
Purchase #7	$97.80	13.470%	$110.9737	$110.97	$110.95	$111.00
7 purchase totals =	$929.83		$991.7637	$991.76	$991.75	$991.90