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	$200.54	9.507%	$219.6053	$219.61	$219.60	$219.60
Purchase #2	$80.26	6.284%	$85.3035	$85.30	$85.30	$85.30
Purchase #3	$147.59	11.379%	$164.3843	$164.38	$164.40	$164.40
Purchase #4	$55.53	13.613%	$63.0893	$63.09	$63.10	$63.10
Purchase #5	$75.92	3.705%	$78.7328	$78.73	$78.75	$78.70
Purchase #6	$151.58	4.300%	$158.0979	$158.10	$158.10	$158.10
Purchase #7	$138.38	4.393%	$144.459	$144.46	$144.45	$144.50
7 purchase totals =	$849.80		$913.6721	$913.67	$913.70	$913.70