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	$42.63	9.208%	$46.5554	$46.56	$46.55	$46.60
Purchase #2	$141.26	8.212%	$152.8603	$152.86	$152.85	$152.90
Purchase #3	$193.44	6.688%	$206.3773	$206.38	$206.40	$206.40
Purchase #4	$134.32	6.322%	$142.8117	$142.81	$142.80	$142.80
Purchase #5	$187.70	4.452%	$196.0564	$196.06	$196.05	$196.10
Purchase #6	$66.50	11.837%	$74.3716	$74.37	$74.35	$74.40
Purchase #7	$221.86	6.496%	$236.272	$236.27	$236.25	$236.30
7 purchase totals =	$987.71		$1,055.3047	$1,055.31	$1,055.25	$1,055.50