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	$156.67	7.641%	$168.6412	$168.64	$168.65	$168.60
Purchase #2	$141.27	13.161%	$159.8625	$159.86	$159.85	$159.90
Purchase #3	$153.34	7.409%	$164.701	$164.70	$164.70	$164.70
Purchase #4	$144.29	12.615%	$162.4922	$162.49	$162.50	$162.50
Purchase #5	$123.37	13.710%	$140.284	$140.28	$140.30	$140.30
Purchase #6	$39.64	8.196%	$42.8889	$42.89	$42.90	$42.90
Purchase #7	$7.35	7.727%	$7.9179	$7.92	$7.90	$7.90
7 purchase totals =	$765.93		$846.7877	$846.78	$846.80	$846.80