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	$49.73	9.331%	$54.3703	$54.37	$54.35	$54.40
Purchase #2	$246.71	9.296%	$269.6442	$269.64	$269.65	$269.60
Purchase #3	$115.40	3.834%	$119.8244	$119.82	$119.80	$119.80
Purchase #4	$137.59	4.519%	$143.8077	$143.81	$143.80	$143.80
Purchase #5	$121.32	3.458%	$125.5152	$125.52	$125.50	$125.50
Purchase #6	$144.94	13.450%	$164.4344	$164.43	$164.45	$164.40
Purchase #7	$117.65	10.870%	$130.4386	$130.44	$130.45	$130.40
7 purchase totals =	$933.34		$1,008.0348	$1,008.03	$1,008.00	$1,007.90