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	$243.37	5.439%	$256.6069	$256.61	$256.60	$256.60
Purchase #2	$86.52	4.537%	$90.4454	$90.45	$90.45	$90.40
Purchase #3	$236.49	9.544%	$259.0606	$259.06	$259.05	$259.10
Purchase #4	$171.52	5.760%	$181.3996	$181.40	$181.40	$181.40
Purchase #5	$55.41	9.171%	$60.4917	$60.49	$60.50	$60.50
Purchase #6	$93.80	8.257%	$101.5451	$101.55	$101.55	$101.50
Purchase #7	$16.31	9.466%	$17.8539	$17.85	$17.85	$17.90
7 purchase totals =	$903.42		$967.4032	$967.41	$967.40	$967.40