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	$95.76	4.437%	$100.0089	$100.01	$100.00	$100.00
Purchase #2	$10.94	13.235%	$12.3879	$12.39	$12.40	$12.40
Purchase #3	$172.43	8.242%	$186.6417	$186.64	$186.65	$186.60
Purchase #4	$31.77	3.833%	$32.9877	$32.99	$33.00	$33.00
Purchase #5	$110.51	11.831%	$123.5844	$123.58	$123.60	$123.60
Purchase #6	$7.25	7.832%	$7.8178	$7.82	$7.80	$7.80
Purchase #7	$160.26	5.250%	$168.6737	$168.67	$168.65	$168.70
7 purchase totals =	$588.92		$632.1021	$632.10	$632.10	$632.10