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	$56.71	8.620%	$61.5984	$61.60	$61.60	$61.60
Purchase #2	$202.90	7.359%	$217.8314	$217.83	$217.85	$217.80
Purchase #3	$90.68	10.455%	$100.1606	$100.16	$100.15	$100.20
Purchase #4	$75.33	7.311%	$80.8374	$80.84	$80.85	$80.80
Purchase #5	$109.75	5.433%	$115.7127	$115.71	$115.70	$115.70
Purchase #6	$218.38	10.787%	$241.9367	$241.94	$241.95	$241.90
Purchase #7	$221.59	7.191%	$237.5245	$237.52	$237.50	$237.50
7 purchase totals =	$975.34		$1,055.6017	$1,055.60	$1,055.60	$1,055.50