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	$167.38	4.724%	$175.287	$175.29	$175.30	$175.30
Purchase #2	$215.57	10.590%	$238.3989	$238.40	$238.40	$238.40
Purchase #3	$95.33	13.627%	$108.3206	$108.32	$108.30	$108.30
Purchase #4	$38.41	5.271%	$40.4346	$40.43	$40.45	$40.40
Purchase #5	$40.56	12.205%	$45.5103	$45.51	$45.50	$45.50
Purchase #6	$114.42	3.379%	$118.2863	$118.29	$118.30	$118.30
Purchase #7	$48.68	5.103%	$51.1641	$51.16	$51.15	$51.20
7 purchase totals =	$720.35		$777.4018	$777.40	$777.40	$777.40