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	$236.57	9.411%	$258.8336	$258.83	$258.85	$258.80
Purchase #2	$227.26	9.592%	$249.0588	$249.06	$249.05	$249.10
Purchase #3	$50.59	9.449%	$55.3702	$55.37	$55.35	$55.40
Purchase #4	$79.28	8.739%	$86.2083	$86.21	$86.20	$86.20
Purchase #5	$182.85	5.724%	$193.3163	$193.32	$193.30	$193.30
Purchase #6	$79.48	5.233%	$83.6392	$83.64	$83.65	$83.60
Purchase #7	$83.59	8.225%	$90.4653	$90.47	$90.45	$90.50
7 purchase totals =	$939.62		$1,016.8917	$1,016.90	$1,016.85	$1,016.90