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	$59.85	6.471%	$63.7229	$63.72	$63.70	$63.70
Purchase #2	$212.60	4.448%	$222.0564	$222.06	$222.05	$222.10
Purchase #3	$40.70	3.298%	$42.0423	$42.04	$42.05	$42.00
Purchase #4	$169.95	8.613%	$184.5878	$184.59	$184.60	$184.60
Purchase #5	$192.46	11.436%	$214.4697	$214.47	$214.45	$214.50
Purchase #6	$89.39	9.849%	$98.194	$98.19	$98.20	$98.20
Purchase #7	$116.94	6.391%	$124.4136	$124.41	$124.40	$124.40
7 purchase totals =	$881.89		$949.4867	$949.48	$949.45	$949.50