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	$94.82	13.359%	$107.487	$107.49	$107.50	$107.50
Purchase #2	$90.59	10.714%	$100.2958	$100.30	$100.30	$100.30
Purchase #3	$49.68	9.745%	$54.5213	$54.52	$54.50	$54.50
Purchase #4	$47.84	10.577%	$52.9	$52.90	$52.90	$52.90
Purchase #5	$118.45	3.296%	$122.3541	$122.35	$122.35	$122.40
Purchase #6	$78.98	4.826%	$82.7916	$82.79	$82.80	$82.80
Purchase #7	$86.44	11.197%	$96.1187	$96.12	$96.10	$96.10
7 purchase totals =	$566.80		$616.4685	$616.47	$616.45	$616.50