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	$95.62	13.509%	$108.5373	$108.54	$108.55	$108.50
Purchase #2	$34.72	9.382%	$37.9774	$37.98	$38.00	$38.00
Purchase #3	$185.42	6.209%	$196.9327	$196.93	$196.95	$196.90
Purchase #4	$76.33	11.445%	$85.066	$85.07	$85.05	$85.10
Purchase #5	$13.65	5.553%	$14.408	$14.41	$14.40	$14.40
Purchase #6	$166.54	3.608%	$172.5488	$172.55	$172.55	$172.50
Purchase #7	$160.62	4.558%	$167.9411	$167.94	$167.95	$167.90
7 purchase totals =	$732.90		$783.4113	$783.42	$783.45	$783.30