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	$221.90	8.874%	$241.5914	$241.59	$241.60	$241.60
Purchase #2	$72.44	7.773%	$78.0708	$78.07	$78.05	$78.10
Purchase #3	$122.46	13.570%	$139.0778	$139.08	$139.10	$139.10
Purchase #4	$237.79	4.546%	$248.5999	$248.60	$248.60	$248.60
Purchase #5	$68.94	5.602%	$72.802	$72.80	$72.80	$72.80
Purchase #6	$108.79	8.321%	$117.8424	$117.84	$117.85	$117.80
Purchase #7	$44.52	3.632%	$46.137	$46.14	$46.15	$46.10
7 purchase totals =	$876.84		$944.1213	$944.12	$944.15	$944.10