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	$60.98	10.122%	$67.1524	$67.15	$67.15	$67.20
Purchase #2	$141.92	8.211%	$153.5731	$153.57	$153.55	$153.60
Purchase #3	$101.74	9.561%	$111.4674	$111.47	$111.45	$111.50
Purchase #4	$222.61	8.291%	$241.0666	$241.07	$241.05	$241.10
Purchase #5	$91.53	4.835%	$95.9555	$95.96	$95.95	$96.00
Purchase #6	$138.86	8.783%	$151.0561	$151.06	$151.05	$151.10
Purchase #7	$160.27	3.459%	$165.8137	$165.81	$165.80	$165.80
7 purchase totals =	$917.91		$986.0848	$986.09	$986.00	$986.30