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	$223.72	13.461%	$253.8349	$253.83	$253.85	$253.80
Purchase #2	$146.56	12.262%	$164.5312	$164.53	$164.55	$164.50
Purchase #3	$10.65	9.153%	$11.6248	$11.62	$11.60	$11.60
Purchase #4	$175.72	6.337%	$186.8554	$186.86	$186.85	$186.90
Purchase #5	$118.54	3.716%	$122.9449	$122.94	$122.95	$122.90
Purchase #6	$68.53	5.539%	$72.3259	$72.33	$72.35	$72.30
Purchase #7	$68.30	6.790%	$72.9376	$72.94	$72.95	$72.90
7 purchase totals =	$812.02		$885.0547	$885.05	$885.10	$884.90