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	$142.93	13.660%	$162.4542	$162.45	$162.45	$162.50
Purchase #2	$6.90	7.724%	$7.433	$7.43	$7.45	$7.40
Purchase #3	$86.81	3.212%	$89.5983	$89.60	$89.60	$89.60
Purchase #4	$43.43	10.278%	$47.8937	$47.89	$47.90	$47.90
Purchase #5	$225.98	12.722%	$254.7292	$254.73	$254.75	$254.70
Purchase #6	$98.72	12.626%	$111.1844	$111.18	$111.20	$111.20
Purchase #7	$160.80	5.744%	$170.0364	$170.04	$170.05	$170.00
7 purchase totals =	$765.57		$843.3292	$843.32	$843.40	$843.30