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	$131.49	10.270%	$144.994	$144.99	$145.00	$145.00
Purchase #2	$19.34	4.210%	$20.1542	$20.15	$20.15	$20.20
Purchase #3	$161.31	9.440%	$176.5377	$176.54	$176.55	$176.50
Purchase #4	$233.80	4.489%	$244.2953	$244.30	$244.30	$244.30
Purchase #5	$69.68	12.534%	$78.4137	$78.41	$78.40	$78.40
Purchase #6	$11.36	10.208%	$12.5196	$12.52	$12.50	$12.50
Purchase #7	$234.36	9.477%	$256.5703	$256.57	$256.55	$256.60
7 purchase totals =	$861.34		$933.4848	$933.48	$933.45	$933.50