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	$177.63	12.280%	$199.443	$199.44	$199.45	$199.40
Purchase #2	$143.32	8.417%	$155.3832	$155.38	$155.40	$155.40
Purchase #3	$121.90	7.649%	$131.2241	$131.22	$131.20	$131.20
Purchase #4	$63.90	11.557%	$71.2849	$71.28	$71.30	$71.30
Purchase #5	$134.54	5.545%	$142.0002	$142.00	$142.00	$142.00
Purchase #6	$164.45	5.716%	$173.85	$173.85	$173.85	$173.90
Purchase #7	$82.57	12.148%	$92.6006	$92.60	$92.60	$92.60
7 purchase totals =	$888.31		$965.7860	$965.77	$965.80	$965.80