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	$20.96	3.515%	$21.6967	$21.70	$21.70	$21.70
Purchase #2	$12.38	4.132%	$12.8915	$12.89	$12.90	$12.90
Purchase #3	$30.31	5.206%	$31.8879	$31.89	$31.90	$31.90
Purchase #4	$57.38	10.217%	$63.2425	$63.24	$63.25	$63.20
Purchase #5	$166.79	11.792%	$186.4579	$186.46	$186.45	$186.50
Purchase #6	$153.63	13.131%	$173.8032	$173.80	$173.80	$173.80
Purchase #7	$193.98	5.429%	$204.5112	$204.51	$204.50	$204.50
7 purchase totals =	$635.43		$694.4909	$694.49	$694.50	$694.50