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	$213.80	11.533%	$238.4576	$238.46	$238.45	$238.50
Purchase #2	$103.75	7.303%	$111.3269	$111.33	$111.35	$111.30
Purchase #3	$71.96	3.139%	$74.2188	$74.22	$74.20	$74.20
Purchase #4	$43.29	7.230%	$46.4199	$46.42	$46.40	$46.40
Purchase #5	$88.75	13.735%	$100.9398	$100.94	$100.95	$100.90
Purchase #6	$131.87	9.565%	$144.4834	$144.48	$144.50	$144.50
Purchase #7	$137.99	3.641%	$143.0142	$143.01	$143.00	$143.00
7 purchase totals =	$791.41		$858.8606	$858.86	$858.85	$858.80