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	$91.37	7.768%	$98.4676	$98.47	$98.45	$98.50
Purchase #2	$20.38	5.476%	$21.496	$21.50	$21.50	$21.50
Purchase #3	$164.45	12.326%	$184.7201	$184.72	$184.70	$184.70
Purchase #4	$207.33	3.564%	$214.7192	$214.72	$214.70	$214.70
Purchase #5	$10.82	7.287%	$11.6085	$11.61	$11.60	$11.60
Purchase #6	$223.62	10.664%	$247.4668	$247.47	$247.45	$247.50
Purchase #7	$85.43	7.611%	$91.9321	$91.93	$91.95	$91.90
7 purchase totals =	$803.40		$870.4103	$870.42	$870.35	$870.40