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	$65.29	9.792%	$71.6832	$71.68	$71.70	$71.70
Purchase #2	$155.25	7.497%	$166.8891	$166.89	$166.90	$166.90
Purchase #3	$64.75	9.395%	$70.8333	$70.83	$70.85	$70.80
Purchase #4	$120.77	4.409%	$126.0947	$126.09	$126.10	$126.10
Purchase #5	$53.84	3.256%	$55.593	$55.59	$55.60	$55.60
Purchase #6	$85.68	4.420%	$89.4671	$89.47	$89.45	$89.50
Purchase #7	$215.86	5.641%	$228.0367	$228.04	$228.05	$228.00
7 purchase totals =	$761.44		$808.5971	$808.59	$808.65	$808.60