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	$175.28	3.718%	$181.7969	$181.80	$181.80	$181.80
Purchase #2	$190.32	10.209%	$209.7498	$209.75	$209.75	$209.70
Purchase #3	$133.52	13.341%	$151.3329	$151.33	$151.35	$151.30
Purchase #4	$134.72	6.683%	$143.7233	$143.72	$143.70	$143.70
Purchase #5	$12.83	3.725%	$13.3079	$13.31	$13.30	$13.30
Purchase #6	$249.55	12.546%	$280.8585	$280.86	$280.85	$280.90
Purchase #7	$73.59	13.492%	$83.5188	$83.52	$83.50	$83.50
7 purchase totals =	$969.81		$1,064.2881	$1,064.29	$1,064.25	$1,064.20