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	$205.47	13.439%	$233.0831	$233.08	$233.10	$233.10
Purchase #2	$102.57	8.725%	$111.5192	$111.52	$111.50	$111.50
Purchase #3	$78.87	13.627%	$89.6176	$89.62	$89.60	$89.60
Purchase #4	$199.40	10.684%	$220.7039	$220.70	$220.70	$220.70
Purchase #5	$228.57	13.866%	$260.2635	$260.26	$260.25	$260.30
Purchase #6	$17.63	6.851%	$18.8378	$18.84	$18.85	$18.80
Purchase #7	$37.85	6.501%	$40.3106	$40.31	$40.30	$40.30
7 purchase totals =	$870.36		$974.3357	$974.33	$974.30	$974.30