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	$163.87	12.627%	$184.5619	$184.56	$184.55	$184.60
Purchase #2	$78.40	5.713%	$82.879	$82.88	$82.90	$82.90
Purchase #3	$240.44	5.797%	$254.3783	$254.38	$254.40	$254.40
Purchase #4	$89.90	11.284%	$100.0443	$100.04	$100.05	$100.00
Purchase #5	$63.58	3.585%	$65.8593	$65.86	$65.85	$65.90
Purchase #6	$8.43	7.716%	$9.0805	$9.08	$9.10	$9.10
Purchase #7	$104.50	13.548%	$118.6577	$118.66	$118.65	$118.70
7 purchase totals =	$749.12		$815.4610	$815.46	$815.50	$815.60