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	$62.54	5.253%	$65.8252	$65.83	$65.85	$65.80
Purchase #2	$164.33	9.676%	$180.2306	$180.23	$180.25	$180.20
Purchase #3	$115.54	13.419%	$131.0443	$131.04	$131.05	$131.00
Purchase #4	$245.86	4.737%	$257.5064	$257.51	$257.50	$257.50
Purchase #5	$101.90	3.598%	$105.5664	$105.57	$105.55	$105.60
Purchase #6	$108.82	3.314%	$112.4263	$112.43	$112.45	$112.40
Purchase #7	$195.90	12.305%	$220.0055	$220.01	$220.00	$220.00
7 purchase totals =	$994.89		$1,072.6047	$1,072.62	$1,072.65	$1,072.50