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	$222.57	4.367%	$232.2896	$232.29	$232.30	$232.30
Purchase #2	$227.39	13.597%	$258.3082	$258.31	$258.30	$258.30
Purchase #3	$206.48	3.670%	$214.0578	$214.06	$214.05	$214.10
Purchase #4	$112.81	10.158%	$124.2692	$124.27	$124.25	$124.30
Purchase #5	$45.34	7.159%	$48.5859	$48.59	$48.60	$48.60
Purchase #6	$148.82	10.433%	$164.3464	$164.35	$164.35	$164.30
Purchase #7	$108.30	7.620%	$116.5525	$116.55	$116.55	$116.60
7 purchase totals =	$1,071.71		$1,158.4096	$1,158.42	$1,158.40	$1,158.50