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	$126.45	10.655%	$139.9232	$139.92	$139.90	$139.90
Purchase #2	$41.89	11.770%	$46.8205	$46.82	$46.80	$46.80
Purchase #3	$94.39	8.511%	$102.4235	$102.42	$102.40	$102.40
Purchase #4	$156.83	6.654%	$167.2655	$167.27	$167.25	$167.30
Purchase #5	$140.52	11.376%	$156.5056	$156.51	$156.50	$156.50
Purchase #6	$192.80	13.446%	$218.7239	$218.72	$218.70	$218.70
Purchase #7	$215.62	11.323%	$240.0347	$240.03	$240.05	$240.00
7 purchase totals =	$968.50		$1,071.6969	$1,071.69	$1,071.60	$1,071.60