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	$119.29	7.205%	$127.8848	$127.88	$127.90	$127.90
Purchase #2	$68.38	4.383%	$71.3771	$71.38	$71.40	$71.40
Purchase #3	$25.49	13.841%	$29.0181	$29.02	$29.00	$29.00
Purchase #4	$62.35	5.459%	$65.7537	$65.75	$65.75	$65.80
Purchase #5	$63.70	4.557%	$66.6028	$66.60	$66.60	$66.60
Purchase #6	$120.27	11.757%	$134.4101	$134.41	$134.40	$134.40
Purchase #7	$112.39	6.302%	$119.4728	$119.47	$119.45	$119.50
7 purchase totals =	$571.87		$614.5194	$614.51	$614.50	$614.60