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	$47.40	9.839%	$52.0637	$52.06	$52.05	$52.10
Purchase #2	$19.63	7.430%	$21.0885	$21.09	$21.10	$21.10
Purchase #3	$13.35	11.455%	$14.8792	$14.88	$14.90	$14.90
Purchase #4	$28.67	8.483%	$31.1021	$31.10	$31.10	$31.10
Purchase #5	$153.32	4.556%	$160.3053	$160.31	$160.30	$160.30
Purchase #6	$97.71	5.198%	$102.789	$102.79	$102.80	$102.80
Purchase #7	$162.56	10.318%	$179.3329	$179.33	$179.35	$179.30
7 purchase totals =	$522.64		$561.5607	$561.56	$561.60	$561.60