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	$41.69	6.862%	$44.5508	$44.55	$44.55	$44.60
Purchase #2	$172.39	9.728%	$189.1601	$189.16	$189.15	$189.20
Purchase #3	$100.56	4.423%	$105.0078	$105.01	$105.00	$105.00
Purchase #4	$237.61	10.487%	$262.5282	$262.53	$262.55	$262.50
Purchase #5	$68.56	5.522%	$72.3459	$72.35	$72.35	$72.30
Purchase #6	$102.60	8.768%	$111.596	$111.60	$111.60	$111.60
Purchase #7	$216.90	12.234%	$243.4355	$243.44	$243.45	$243.40
7 purchase totals =	$940.31		$1,028.6243	$1,028.64	$1,028.65	$1,028.60