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	$106.59	5.477%	$112.4279	$112.43	$112.45	$112.40
Purchase #2	$183.40	3.297%	$189.4467	$189.45	$189.45	$189.40
Purchase #3	$137.68	6.793%	$147.0326	$147.03	$147.05	$147.00
Purchase #4	$226.90	11.526%	$253.0525	$253.05	$253.05	$253.10
Purchase #5	$111.76	6.629%	$119.1686	$119.17	$119.15	$119.20
Purchase #6	$124.79	7.602%	$134.2765	$134.28	$134.30	$134.30
Purchase #7	$56.35	8.397%	$61.0817	$61.08	$61.10	$61.10
7 purchase totals =	$947.47		$1,016.4865	$1,016.49	$1,016.55	$1,016.50