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	$52.64	13.264%	$59.6222	$59.62	$59.60	$59.60
Purchase #2	$105.79	5.288%	$111.3842	$111.38	$111.40	$111.40
Purchase #3	$67.38	8.622%	$73.1895	$73.19	$73.20	$73.20
Purchase #4	$71.54	10.392%	$78.9744	$78.97	$78.95	$79.00
Purchase #5	$49.92	13.691%	$56.7545	$56.75	$56.75	$56.80
Purchase #6	$208.86	12.595%	$235.1659	$235.17	$235.15	$235.20
Purchase #7	$131.43	10.194%	$144.828	$144.83	$144.85	$144.80
7 purchase totals =	$687.56		$759.9187	$759.91	$759.90	$760.00