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	$56.81	10.799%	$62.9449	$62.94	$62.95	$62.90
Purchase #2	$157.40	9.372%	$172.1515	$172.15	$172.15	$172.20
Purchase #3	$81.26	11.239%	$90.3928	$90.39	$90.40	$90.40
Purchase #4	$96.46	10.450%	$106.5401	$106.54	$106.55	$106.50
Purchase #5	$200.62	4.471%	$209.5897	$209.59	$209.60	$209.60
Purchase #6	$116.74	8.397%	$126.5427	$126.54	$126.55	$126.50
Purchase #7	$6.90	8.455%	$7.4834	$7.48	$7.50	$7.50
7 purchase totals =	$716.19		$775.6451	$775.63	$775.70	$775.60