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	$8.41	12.641%	$9.4731	$9.47	$9.45	$9.50
Purchase #2	$178.94	9.745%	$196.3777	$196.38	$196.40	$196.40
Purchase #3	$59.33	7.499%	$63.7792	$63.78	$63.80	$63.80
Purchase #4	$48.80	10.166%	$53.761	$53.76	$53.75	$53.80
Purchase #5	$210.56	9.612%	$230.799	$230.80	$230.80	$230.80
Purchase #6	$149.85	5.367%	$157.8924	$157.89	$157.90	$157.90
Purchase #7	$146.67	6.619%	$156.3781	$156.38	$156.40	$156.40
7 purchase totals =	$802.56		$868.4605	$868.46	$868.50	$868.60