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	$71.49	10.227%	$78.8013	$78.80	$78.80	$78.80
Purchase #2	$20.50	4.606%	$21.4442	$21.44	$21.45	$21.40
Purchase #3	$84.35	13.209%	$95.4918	$95.49	$95.50	$95.50
Purchase #4	$45.77	11.175%	$50.8848	$50.88	$50.90	$50.90
Purchase #5	$192.58	6.711%	$205.504	$205.50	$205.50	$205.50
Purchase #6	$219.62	9.322%	$240.093	$240.09	$240.10	$240.10
Purchase #7	$31.51	10.648%	$34.8652	$34.87	$34.85	$34.90
7 purchase totals =	$665.82		$727.0843	$727.07	$727.10	$727.10