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	$100.87	10.121%	$111.0791	$111.08	$111.10	$111.10
Purchase #2	$100.60	12.332%	$113.006	$113.01	$113.00	$113.00
Purchase #3	$180.50	6.591%	$192.3968	$192.40	$192.40	$192.40
Purchase #4	$240.85	6.576%	$256.6883	$256.69	$256.70	$256.70
Purchase #5	$136.73	4.123%	$142.3674	$142.37	$142.35	$142.40
Purchase #6	$143.48	5.138%	$150.852	$150.85	$150.85	$150.90
Purchase #7	$48.53	8.427%	$52.6196	$52.62	$52.60	$52.60
7 purchase totals =	$951.56		$1,019.0092	$1,019.02	$1,019.00	$1,019.10