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	$196.82	4.586%	$205.8462	$205.85	$205.85	$205.80
Purchase #2	$178.64	4.136%	$186.0286	$186.03	$186.05	$186.00
Purchase #3	$246.65	3.531%	$255.3592	$255.36	$255.35	$255.40
Purchase #4	$103.85	10.625%	$114.8841	$114.88	$114.90	$114.90
Purchase #5	$68.77	4.820%	$72.0847	$72.08	$72.10	$72.10
Purchase #6	$5.96	5.379%	$6.2806	$6.28	$6.30	$6.30
Purchase #7	$57.94	8.473%	$62.8493	$62.85	$62.85	$62.80
7 purchase totals =	$858.63		$903.3327	$903.33	$903.40	$903.30