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	$22.69	4.509%	$23.7131	$23.71	$23.70	$23.70
Purchase #2	$33.31	4.387%	$34.7713	$34.77	$34.75	$34.80
Purchase #3	$23.95	13.558%	$27.1971	$27.20	$27.20	$27.20
Purchase #4	$172.74	13.483%	$196.0305	$196.03	$196.05	$196.00
Purchase #5	$96.60	13.468%	$109.6101	$109.61	$109.60	$109.60
Purchase #6	$186.50	6.240%	$198.1376	$198.14	$198.15	$198.10
Purchase #7	$226.88	12.385%	$254.9791	$254.98	$255.00	$255.00
7 purchase totals =	$762.67		$844.4388	$844.44	$844.45	$844.40