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	$64.81	9.319%	$70.8496	$70.85	$70.85	$70.80
Purchase #2	$67.72	10.193%	$74.6227	$74.62	$74.60	$74.60
Purchase #3	$191.61	12.516%	$215.5919	$215.59	$215.60	$215.60
Purchase #4	$78.69	12.488%	$88.5168	$88.52	$88.50	$88.50
Purchase #5	$196.60	10.495%	$217.2332	$217.23	$217.25	$217.20
Purchase #6	$157.67	9.811%	$173.139	$173.14	$173.15	$173.10
Purchase #7	$123.91	11.409%	$138.0469	$138.05	$138.05	$138.00
7 purchase totals =	$881.01		$978.0001	$978.00	$978.00	$977.80