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	$154.78	8.453%	$167.8636	$167.86	$167.85	$167.90
Purchase #2	$75.49	9.636%	$82.7642	$82.76	$82.75	$82.80
Purchase #3	$15.41	13.557%	$17.4991	$17.50	$17.50	$17.50
Purchase #4	$101.70	12.626%	$114.5406	$114.54	$114.55	$114.50
Purchase #5	$45.52	13.504%	$51.667	$51.67	$51.65	$51.70
Purchase #6	$89.37	3.549%	$92.5417	$92.54	$92.55	$92.50
Purchase #7	$73.78	10.357%	$81.4214	$81.42	$81.40	$81.40
7 purchase totals =	$556.05		$608.2976	$608.29	$608.25	$608.30