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	$127.61	12.399%	$143.4324	$143.43	$143.45	$143.40
Purchase #2	$202.46	11.528%	$225.7996	$225.80	$225.80	$225.80
Purchase #3	$44.86	6.446%	$47.7517	$47.75	$47.75	$47.80
Purchase #4	$155.61	10.807%	$172.4268	$172.43	$172.45	$172.40
Purchase #5	$164.80	10.233%	$181.664	$181.66	$181.65	$181.70
Purchase #6	$19.72	3.292%	$20.3692	$20.37	$20.35	$20.40
Purchase #7	$161.31	6.269%	$171.4225	$171.42	$171.40	$171.40
7 purchase totals =	$876.37		$962.8662	$962.86	$962.85	$962.90