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	$98.60	10.258%	$108.7144	$108.71	$108.70	$108.70
Purchase #2	$85.43	11.247%	$95.0383	$95.04	$95.05	$95.00
Purchase #3	$238.98	6.332%	$254.1122	$254.11	$254.10	$254.10
Purchase #4	$74.25	12.714%	$83.6901	$83.69	$83.70	$83.70
Purchase #5	$122.94	3.701%	$127.49	$127.49	$127.50	$127.50
Purchase #6	$227.74	12.311%	$255.7771	$255.78	$255.80	$255.80
Purchase #7	$139.88	9.874%	$153.6918	$153.69	$153.70	$153.70
7 purchase totals =	$987.82		$1,078.5139	$1,078.51	$1,078.55	$1,078.50