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	$119.28	13.616%	$135.5212	$135.52	$135.50	$135.50
Purchase #2	$71.60	9.588%	$78.465	$78.47	$78.45	$78.50
Purchase #3	$48.56	6.791%	$51.8577	$51.86	$51.85	$51.90
Purchase #4	$180.32	10.641%	$199.5079	$199.51	$199.50	$199.50
Purchase #5	$183.55	3.522%	$190.0146	$190.01	$190.00	$190.00
Purchase #6	$155.32	10.238%	$171.2217	$171.22	$171.20	$171.20
Purchase #7	$161.66	12.138%	$181.2823	$181.28	$181.30	$181.30
7 purchase totals =	$920.29		$1,007.8704	$1,007.87	$1,007.80	$1,007.90