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	$10.85	6.724%	$11.5796	$11.58	$11.60	$11.60
Purchase #2	$61.92	4.157%	$64.494	$64.49	$64.50	$64.50
Purchase #3	$61.43	3.204%	$63.3982	$63.40	$63.40	$63.40
Purchase #4	$12.72	6.662%	$13.5674	$13.57	$13.55	$13.60
Purchase #5	$54.60	11.422%	$60.8364	$60.84	$60.85	$60.80
Purchase #6	$76.34	8.374%	$82.7327	$82.73	$82.75	$82.70
Purchase #7	$143.63	13.421%	$162.9066	$162.91	$162.90	$162.90
7 purchase totals =	$421.49		$459.5149	$459.52	$459.55	$459.50