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	$249.63	3.777%	$259.0585	$259.06	$259.05	$259.10
Purchase #2	$205.34	8.643%	$223.0875	$223.09	$223.10	$223.10
Purchase #3	$78.55	4.863%	$82.3699	$82.37	$82.35	$82.40
Purchase #4	$194.88	13.599%	$221.3817	$221.38	$221.40	$221.40
Purchase #5	$130.47	5.264%	$137.3379	$137.34	$137.35	$137.30
Purchase #6	$145.35	6.515%	$154.8196	$154.82	$154.80	$154.80
Purchase #7	$129.34	7.796%	$139.4233	$139.42	$139.40	$139.40
7 purchase totals =	$1,133.56		$1,217.4784	$1,217.48	$1,217.45	$1,217.50