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	$212.47	3.787%	$220.5162	$220.52	$220.50	$220.50
Purchase #2	$115.25	9.775%	$126.5157	$126.52	$126.50	$126.50
Purchase #3	$121.44	8.127%	$131.3094	$131.31	$131.30	$131.30
Purchase #4	$134.63	7.262%	$144.4068	$144.41	$144.40	$144.40
Purchase #5	$100.56	5.236%	$105.8253	$105.83	$105.85	$105.80
Purchase #6	$44.77	11.827%	$50.0649	$50.06	$50.05	$50.10
Purchase #7	$163.31	6.258%	$173.5299	$173.53	$173.55	$173.50
7 purchase totals =	$892.43		$952.1682	$952.18	$952.15	$952.10