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	$17.90	8.566%	$19.4333	$19.43	$19.45	$19.40
Purchase #2	$100.33	11.104%	$111.4706	$111.47	$111.45	$111.50
Purchase #3	$183.72	4.329%	$191.6732	$191.67	$191.65	$191.70
Purchase #4	$231.28	13.484%	$262.4658	$262.47	$262.45	$262.50
Purchase #5	$92.63	6.445%	$98.6	$98.60	$98.60	$98.60
Purchase #6	$149.32	11.850%	$167.0144	$167.01	$167.00	$167.00
Purchase #7	$223.82	11.151%	$248.7782	$248.78	$248.80	$248.80
7 purchase totals =	$999.00		$1,099.4355	$1,099.43	$1,099.40	$1,099.50