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	$152.89	9.473%	$167.3733	$167.37	$167.35	$167.40
Purchase #2	$128.85	12.423%	$144.857	$144.86	$144.85	$144.90
Purchase #3	$145.97	3.824%	$151.5519	$151.55	$151.55	$151.60
Purchase #4	$154.35	7.246%	$165.5342	$165.53	$165.55	$165.50
Purchase #5	$143.89	6.683%	$153.5062	$153.51	$153.50	$153.50
Purchase #6	$38.61	4.497%	$40.3463	$40.35	$40.35	$40.30
Purchase #7	$39.28	3.774%	$40.7624	$40.76	$40.75	$40.80
7 purchase totals =	$803.84		$863.9313	$863.93	$863.90	$864.00