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	$238.69	9.553%	$261.4921	$261.49	$261.50	$261.50
Purchase #2	$79.71	3.471%	$82.4767	$82.48	$82.50	$82.50
Purchase #3	$76.28	7.839%	$82.2596	$82.26	$82.25	$82.30
Purchase #4	$239.61	7.589%	$257.794	$257.79	$257.80	$257.80
Purchase #5	$114.80	7.155%	$123.0139	$123.01	$123.00	$123.00
Purchase #6	$127.99	13.648%	$145.4581	$145.46	$145.45	$145.50
Purchase #7	$226.81	13.326%	$257.0347	$257.03	$257.05	$257.00
7 purchase totals =	$1,103.89		$1,209.5291	$1,209.52	$1,209.55	$1,209.60