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	$139.82	11.763%	$156.267	$156.27	$156.25	$156.30
Purchase #2	$178.94	4.446%	$186.8957	$186.90	$186.90	$186.90
Purchase #3	$50.75	8.308%	$54.9663	$54.97	$54.95	$55.00
Purchase #4	$31.34	13.564%	$35.591	$35.59	$35.60	$35.60
Purchase #5	$115.30	7.195%	$123.5958	$123.60	$123.60	$123.60
Purchase #6	$42.77	6.163%	$45.4059	$45.41	$45.40	$45.40
Purchase #7	$112.43	3.495%	$116.3594	$116.36	$116.35	$116.40
7 purchase totals =	$671.35		$719.0811	$719.10	$719.05	$719.20