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	$153.31	7.256%	$164.4342	$164.43	$164.45	$164.40
Purchase #2	$131.59	8.171%	$142.3422	$142.34	$142.35	$142.30
Purchase #3	$72.86	8.485%	$79.0422	$79.04	$79.05	$79.00
Purchase #4	$198.83	13.558%	$225.7874	$225.79	$225.80	$225.80
Purchase #5	$163.93	9.530%	$179.5525	$179.55	$179.55	$179.60
Purchase #6	$177.60	6.151%	$188.5242	$188.52	$188.50	$188.50
Purchase #7	$68.95	13.487%	$78.2493	$78.25	$78.25	$78.20
7 purchase totals =	$967.07		$1,057.9320	$1,057.92	$1,057.95	$1,057.80