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	$101.30	9.770%	$111.197	$111.20	$111.20	$111.20
Purchase #2	$88.58	13.690%	$100.7066	$100.71	$100.70	$100.70
Purchase #3	$79.83	3.661%	$82.7526	$82.75	$82.75	$82.80
Purchase #4	$10.80	3.832%	$11.2139	$11.21	$11.20	$11.20
Purchase #5	$180.48	3.636%	$187.0423	$187.04	$187.05	$187.00
Purchase #6	$38.57	5.243%	$40.5922	$40.59	$40.60	$40.60
Purchase #7	$187.73	12.451%	$211.1043	$211.10	$211.10	$211.10
7 purchase totals =	$687.29		$744.6089	$744.60	$744.60	$744.60