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	$38.79	9.170%	$42.347	$42.35	$42.35	$42.30
Purchase #2	$44.78	6.141%	$47.5299	$47.53	$47.55	$47.50
Purchase #3	$60.84	3.474%	$62.9536	$62.95	$62.95	$63.00
Purchase #4	$165.39	5.698%	$174.8139	$174.81	$174.80	$174.80
Purchase #5	$92.91	13.671%	$105.6117	$105.61	$105.60	$105.60
Purchase #6	$132.91	3.419%	$137.4542	$137.45	$137.45	$137.50
Purchase #7	$157.88	6.102%	$167.5138	$167.51	$167.50	$167.50
7 purchase totals =	$693.50		$738.2241	$738.21	$738.20	$738.20