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	$91.61	13.458%	$103.9389	$103.94	$103.95	$103.90
Purchase #2	$20.33	13.591%	$23.0931	$23.09	$23.10	$23.10
Purchase #3	$173.66	4.379%	$181.2646	$181.26	$181.25	$181.30
Purchase #4	$154.94	11.332%	$172.4978	$172.50	$172.50	$172.50
Purchase #5	$73.86	13.641%	$83.9352	$83.94	$83.95	$83.90
Purchase #6	$72.79	9.341%	$79.5893	$79.59	$79.60	$79.60
Purchase #7	$238.59	3.106%	$246.0006	$246.00	$246.00	$246.00
7 purchase totals =	$825.78		$890.3195	$890.32	$890.35	$890.30