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	$243.35	13.441%	$276.0587	$276.06	$276.05	$276.10
Purchase #2	$161.74	6.422%	$172.1269	$172.13	$172.15	$172.10
Purchase #3	$203.67	7.859%	$219.6764	$219.68	$219.70	$219.70
Purchase #4	$118.54	3.780%	$123.0208	$123.02	$123.00	$123.00
Purchase #5	$126.78	12.206%	$142.2548	$142.25	$142.25	$142.30
Purchase #6	$112.87	9.509%	$123.6028	$123.60	$123.60	$123.60
Purchase #7	$174.30	3.181%	$179.8445	$179.84	$179.85	$179.80
7 purchase totals =	$1,141.25		$1,236.5849	$1,236.58	$1,236.60	$1,236.60