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	$239.89	10.504%	$265.088	$265.09	$265.10	$265.10
Purchase #2	$117.90	10.201%	$129.927	$129.93	$129.95	$129.90
Purchase #3	$126.73	6.180%	$134.5619	$134.56	$134.55	$134.60
Purchase #4	$146.82	4.343%	$153.1964	$153.20	$153.20	$153.20
Purchase #5	$165.39	4.682%	$173.1336	$173.13	$173.15	$173.10
Purchase #6	$133.43	4.767%	$139.7906	$139.79	$139.80	$139.80
Purchase #7	$158.89	6.255%	$168.8286	$168.83	$168.85	$168.80
7 purchase totals =	$1,089.05		$1,164.5261	$1,164.53	$1,164.60	$1,164.50