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	$96.35	12.202%	$108.1066	$108.11	$108.10	$108.10
Purchase #2	$81.86	9.445%	$89.5917	$89.59	$89.60	$89.60
Purchase #3	$226.58	13.758%	$257.7529	$257.75	$257.75	$257.80
Purchase #4	$232.86	11.780%	$260.2909	$260.29	$260.30	$260.30
Purchase #5	$143.29	13.397%	$162.4866	$162.49	$162.50	$162.50
Purchase #6	$111.38	4.653%	$116.5625	$116.56	$116.55	$116.60
Purchase #7	$112.42	4.418%	$117.3867	$117.39	$117.40	$117.40
7 purchase totals =	$1,004.74		$1,112.1779	$1,112.18	$1,112.20	$1,112.30