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	$62.60	10.677%	$69.2838	$69.28	$69.30	$69.30
Purchase #2	$249.70	13.219%	$282.7078	$282.71	$282.70	$282.70
Purchase #3	$66.50	9.779%	$73.003	$73.00	$73.00	$73.00
Purchase #4	$72.62	8.620%	$78.8798	$78.88	$78.90	$78.90
Purchase #5	$103.58	7.748%	$111.6054	$111.61	$111.60	$111.60
Purchase #6	$222.86	7.819%	$240.2854	$240.29	$240.30	$240.30
Purchase #7	$238.31	9.344%	$260.5777	$260.58	$260.60	$260.60
7 purchase totals =	$1,016.17		$1,116.3429	$1,116.35	$1,116.40	$1,116.40