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	$111.56	6.417%	$118.7188	$118.72	$118.70	$118.70
Purchase #2	$43.25	5.420%	$45.5942	$45.59	$45.60	$45.60
Purchase #3	$13.92	11.670%	$15.5445	$15.54	$15.55	$15.50
Purchase #4	$242.94	9.236%	$265.3779	$265.38	$265.40	$265.40
Purchase #5	$119.90	10.409%	$132.3804	$132.38	$132.40	$132.40
Purchase #6	$234.77	8.638%	$255.0494	$255.05	$255.05	$255.00
Purchase #7	$103.30	6.296%	$109.8038	$109.80	$109.80	$109.80
7 purchase totals =	$869.64		$942.4690	$942.46	$942.50	$942.40