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	$71.50	7.670%	$76.9841	$76.98	$77.00	$77.00
Purchase #2	$192.29	12.191%	$215.7321	$215.73	$215.75	$215.70
Purchase #3	$185.92	5.523%	$196.1884	$196.19	$196.20	$196.20
Purchase #4	$108.95	9.607%	$119.4168	$119.42	$119.40	$119.40
Purchase #5	$32.29	7.200%	$34.6149	$34.61	$34.60	$34.60
Purchase #6	$226.68	12.857%	$255.8242	$255.82	$255.80	$255.80
Purchase #7	$35.52	11.782%	$39.705	$39.71	$39.70	$39.70
7 purchase totals =	$853.15		$938.4655	$938.46	$938.45	$938.40