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	$191.34	9.669%	$209.8407	$209.84	$209.85	$209.80
Purchase #2	$96.45	5.821%	$102.0644	$102.06	$102.05	$102.10
Purchase #3	$128.78	6.836%	$137.5834	$137.58	$137.60	$137.60
Purchase #4	$222.86	8.495%	$241.792	$241.79	$241.80	$241.80
Purchase #5	$165.69	6.681%	$176.7597	$176.76	$176.75	$176.80
Purchase #6	$75.27	9.754%	$82.6118	$82.61	$82.60	$82.60
Purchase #7	$105.64	4.789%	$110.6991	$110.70	$110.70	$110.70
7 purchase totals =	$986.03		$1,061.3511	$1,061.34	$1,061.35	$1,061.40