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	$174.77	3.781%	$181.3781	$181.38	$181.40	$181.40
Purchase #2	$39.80	10.186%	$43.854	$43.85	$43.85	$43.90
Purchase #3	$40.45	12.278%	$45.4165	$45.42	$45.40	$45.40
Purchase #4	$18.31	8.398%	$19.8477	$19.85	$19.85	$19.80
Purchase #5	$198.26	3.697%	$205.5897	$205.59	$205.60	$205.60
Purchase #6	$208.85	5.271%	$219.8585	$219.86	$219.85	$219.90
Purchase #7	$222.81	9.350%	$243.6427	$243.64	$243.65	$243.60
7 purchase totals =	$903.25		$959.5872	$959.59	$959.60	$959.60