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	$84.41	13.728%	$95.9978	$96.00	$96.00	$96.00
Purchase #2	$44.38	3.339%	$45.8618	$45.86	$45.85	$45.90
Purchase #3	$155.85	8.122%	$168.5081	$168.51	$168.50	$168.50
Purchase #4	$130.34	11.169%	$144.8977	$144.90	$144.90	$144.90
Purchase #5	$11.71	13.461%	$13.2863	$13.29	$13.30	$13.30
Purchase #6	$147.89	4.498%	$154.5421	$154.54	$154.55	$154.50
Purchase #7	$156.30	11.195%	$173.7978	$173.80	$173.80	$173.80
7 purchase totals =	$730.88		$796.8916	$796.90	$796.90	$796.90