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	$208.55	3.540%	$215.9327	$215.93	$215.95	$215.90
Purchase #2	$86.64	4.185%	$90.2659	$90.27	$90.25	$90.30
Purchase #3	$20.40	8.129%	$22.0583	$22.06	$22.05	$22.10
Purchase #4	$236.71	8.326%	$256.4185	$256.42	$256.40	$256.40
Purchase #5	$24.86	10.207%	$27.3975	$27.40	$27.40	$27.40
Purchase #6	$101.76	6.635%	$108.5118	$108.51	$108.50	$108.50
Purchase #7	$115.65	13.576%	$131.3506	$131.35	$131.35	$131.40
7 purchase totals =	$794.57		$851.9353	$851.94	$851.90	$852.00