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	$57.41	4.393%	$59.932	$59.93	$59.95	$59.90
Purchase #2	$244.51	5.724%	$258.5058	$258.51	$258.50	$258.50
Purchase #3	$74.85	4.618%	$78.3066	$78.31	$78.30	$78.30
Purchase #4	$155.50	5.857%	$164.6076	$164.61	$164.60	$164.60
Purchase #5	$138.60	4.405%	$144.7053	$144.71	$144.70	$144.70
Purchase #6	$135.42	12.172%	$151.9033	$151.90	$151.90	$151.90
Purchase #7	$176.52	10.670%	$195.3547	$195.35	$195.35	$195.40
7 purchase totals =	$982.81		$1,053.3153	$1,053.32	$1,053.30	$1,053.30