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	$153.40	5.118%	$161.251	$161.25	$161.25	$161.30
Purchase #2	$136.90	11.778%	$153.0241	$153.02	$153.00	$153.00
Purchase #3	$61.58	3.333%	$63.6325	$63.63	$63.65	$63.60
Purchase #4	$29.98	7.732%	$32.2981	$32.30	$32.30	$32.30
Purchase #5	$31.26	9.198%	$34.1353	$34.14	$34.15	$34.10
Purchase #6	$52.38	13.766%	$59.5906	$59.59	$59.60	$59.60
Purchase #7	$59.90	4.264%	$62.4541	$62.45	$62.45	$62.50
7 purchase totals =	$525.40		$566.3857	$566.38	$566.40	$566.40