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	$196.25	9.857%	$215.5944	$215.59	$215.60	$215.60
Purchase #2	$214.55	7.415%	$230.4589	$230.46	$230.45	$230.50
Purchase #3	$152.40	9.455%	$166.8094	$166.81	$166.80	$166.80
Purchase #4	$134.30	7.764%	$144.7271	$144.73	$144.75	$144.70
Purchase #5	$178.87	3.752%	$185.5812	$185.58	$185.60	$185.60
Purchase #6	$60.62	12.225%	$68.0308	$68.03	$68.05	$68.00
Purchase #7	$102.70	8.342%	$111.2672	$111.27	$111.25	$111.30
7 purchase totals =	$1,039.69		$1,122.4690	$1,122.47	$1,122.50	$1,122.50