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	$54.64	11.661%	$61.0116	$61.01	$61.00	$61.00
Purchase #2	$117.72	12.112%	$131.9782	$131.98	$132.00	$132.00
Purchase #3	$134.78	8.274%	$145.9317	$145.93	$145.95	$145.90
Purchase #4	$162.31	8.600%	$176.2687	$176.27	$176.25	$176.30
Purchase #5	$116.76	12.641%	$131.5196	$131.52	$131.50	$131.50
Purchase #6	$49.36	9.487%	$54.0428	$54.04	$54.05	$54.00
Purchase #7	$23.83	13.531%	$27.0544	$27.05	$27.05	$27.10
7 purchase totals =	$659.40		$727.8070	$727.80	$727.80	$727.80