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	$104.92	13.509%	$119.0936	$119.09	$119.10	$119.10
Purchase #2	$46.43	11.601%	$51.8163	$51.82	$51.80	$51.80
Purchase #3	$106.80	4.211%	$111.2973	$111.30	$111.30	$111.30
Purchase #4	$61.91	4.593%	$64.7535	$64.75	$64.75	$64.80
Purchase #5	$42.53	4.577%	$44.4766	$44.48	$44.50	$44.50
Purchase #6	$228.88	12.155%	$256.7004	$256.70	$256.70	$256.70
Purchase #7	$202.29	13.850%	$230.3072	$230.31	$230.30	$230.30
7 purchase totals =	$793.76		$878.4449	$878.45	$878.45	$878.50