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	$121.88	7.666%	$131.2233	$131.22	$131.20	$131.20
Purchase #2	$195.97	10.450%	$216.4489	$216.45	$216.45	$216.40
Purchase #3	$12.93	8.704%	$14.0554	$14.06	$14.05	$14.10
Purchase #4	$213.95	6.503%	$227.8632	$227.86	$227.85	$227.90
Purchase #5	$154.61	7.748%	$166.5892	$166.59	$166.60	$166.60
Purchase #6	$96.27	4.848%	$100.9372	$100.94	$100.95	$100.90
Purchase #7	$244.96	13.848%	$278.8821	$278.88	$278.90	$278.90
7 purchase totals =	$1,040.57		$1,135.9993	$1,136.00	$1,136.00	$1,136.00