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	$229.50	11.116%	$255.0112	$255.01	$255.00	$255.00
Purchase #2	$11.88	13.348%	$13.4657	$13.47	$13.45	$13.50
Purchase #3	$154.52	7.775%	$166.5339	$166.53	$166.55	$166.50
Purchase #4	$199.99	9.466%	$218.9211	$218.92	$218.90	$218.90
Purchase #5	$107.30	3.519%	$111.0759	$111.08	$111.10	$111.10
Purchase #6	$125.46	13.412%	$142.2867	$142.29	$142.30	$142.30
Purchase #7	$101.35	3.372%	$104.7675	$104.77	$104.75	$104.80
7 purchase totals =	$930.00		$1,012.0620	$1,012.07	$1,012.05	$1,012.10