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	$115.85	13.455%	$131.4376	$131.44	$131.45	$131.40
Purchase #2	$26.48	5.515%	$27.9404	$27.94	$27.95	$27.90
Purchase #3	$148.77	12.188%	$166.9021	$166.90	$166.90	$166.90
Purchase #4	$181.54	9.307%	$198.4359	$198.44	$198.45	$198.40
Purchase #5	$39.46	3.443%	$40.8186	$40.82	$40.80	$40.80
Purchase #6	$79.60	13.412%	$90.276	$90.28	$90.30	$90.30
Purchase #7	$90.83	11.292%	$101.0865	$101.09	$101.10	$101.10
7 purchase totals =	$682.53		$756.8971	$756.91	$756.95	$756.80