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	$103.67	13.798%	$117.9744	$117.97	$117.95	$118.00
Purchase #2	$48.84	11.491%	$54.4522	$54.45	$54.45	$54.50
Purchase #3	$76.80	13.724%	$87.34	$87.34	$87.35	$87.30
Purchase #4	$59.25	13.398%	$67.1883	$67.19	$67.20	$67.20
Purchase #5	$67.43	7.542%	$72.5156	$72.52	$72.50	$72.50
Purchase #6	$236.65	11.270%	$263.3205	$263.32	$263.30	$263.30
Purchase #7	$76.43	7.305%	$82.0132	$82.01	$82.00	$82.00
7 purchase totals =	$669.07		$744.8042	$744.80	$744.75	$744.80