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	$210.66	12.553%	$237.1041	$237.10	$237.10	$237.10
Purchase #2	$89.46	12.438%	$100.587	$100.59	$100.60	$100.60
Purchase #3	$205.52	3.537%	$212.7892	$212.79	$212.80	$212.80
Purchase #4	$134.45	3.462%	$139.1047	$139.10	$139.10	$139.10
Purchase #5	$52.25	13.313%	$59.206	$59.21	$59.20	$59.20
Purchase #6	$87.65	10.711%	$97.0382	$97.04	$97.05	$97.00
Purchase #7	$142.94	12.353%	$160.5974	$160.60	$160.60	$160.60
7 purchase totals =	$922.93		$1,006.4266	$1,006.43	$1,006.45	$1,006.40