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	$36.71	5.514%	$38.7342	$38.73	$38.75	$38.70
Purchase #2	$58.51	11.872%	$65.4563	$65.46	$65.45	$65.50
Purchase #3	$9.49	9.358%	$10.3781	$10.38	$10.40	$10.40
Purchase #4	$39.55	7.846%	$42.6531	$42.65	$42.65	$42.70
Purchase #5	$214.41	11.121%	$238.2545	$238.25	$238.25	$238.30
Purchase #6	$64.80	6.724%	$69.1572	$69.16	$69.15	$69.20
Purchase #7	$247.27	3.301%	$255.4324	$255.43	$255.45	$255.40
7 purchase totals =	$670.74		$720.0658	$720.06	$720.10	$720.20