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	$160.33	7.403%	$172.1992	$172.20	$172.20	$172.20
Purchase #2	$149.28	10.569%	$165.0574	$165.06	$165.05	$165.10
Purchase #3	$155.90	6.170%	$165.519	$165.52	$165.50	$165.50
Purchase #4	$12.38	10.368%	$13.6636	$13.66	$13.65	$13.70
Purchase #5	$117.56	4.624%	$122.996	$123.00	$123.00	$123.00
Purchase #6	$211.52	9.633%	$231.8957	$231.90	$231.90	$231.90
Purchase #7	$171.65	9.620%	$188.1627	$188.16	$188.15	$188.20
7 purchase totals =	$978.62		$1,059.4936	$1,059.50	$1,059.45	$1,059.60