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	$149.83	9.759%	$164.4519	$164.45	$164.45	$164.50
Purchase #2	$11.60	3.845%	$12.046	$12.05	$12.05	$12.00
Purchase #3	$73.98	10.697%	$81.8936	$81.89	$81.90	$81.90
Purchase #4	$50.25	12.356%	$56.4589	$56.46	$56.45	$56.50
Purchase #5	$238.82	5.841%	$252.7695	$252.77	$252.75	$252.80
Purchase #6	$92.41	6.572%	$98.4832	$98.48	$98.50	$98.50
Purchase #7	$224.80	3.111%	$231.7935	$231.79	$231.80	$231.80
7 purchase totals =	$841.69		$897.8966	$897.89	$897.90	$898.00