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	$151.28	11.873%	$169.2415	$169.24	$169.25	$169.20
Purchase #2	$119.67	5.860%	$126.6827	$126.68	$126.70	$126.70
Purchase #3	$155.27	5.712%	$164.139	$164.14	$164.15	$164.10
Purchase #4	$104.52	11.469%	$116.5074	$116.51	$116.50	$116.50
Purchase #5	$53.63	10.379%	$59.1963	$59.20	$59.20	$59.20
Purchase #6	$166.85	3.307%	$172.3677	$172.37	$172.35	$172.40
Purchase #7	$213.45	3.191%	$220.2612	$220.26	$220.25	$220.30
7 purchase totals =	$964.67		$1,028.3958	$1,028.40	$1,028.40	$1,028.40