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	$113.79	11.637%	$127.0317	$127.03	$127.05	$127.00
Purchase #2	$202.87	3.643%	$210.2606	$210.26	$210.25	$210.30
Purchase #3	$145.38	13.299%	$164.7141	$164.71	$164.70	$164.70
Purchase #4	$80.39	11.252%	$89.4355	$89.44	$89.45	$89.40
Purchase #5	$77.27	4.665%	$80.8746	$80.87	$80.85	$80.90
Purchase #6	$136.30	12.527%	$153.3743	$153.37	$153.35	$153.40
Purchase #7	$238.52	8.121%	$257.8902	$257.89	$257.90	$257.90
7 purchase totals =	$994.52		$1,083.5810	$1,083.57	$1,083.55	$1,083.60