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	$205.37	13.171%	$232.4193	$232.42	$232.40	$232.40
Purchase #2	$171.83	8.672%	$186.7311	$186.73	$186.75	$186.70
Purchase #3	$51.70	9.475%	$56.5986	$56.60	$56.60	$56.60
Purchase #4	$80.45	11.363%	$89.5915	$89.59	$89.60	$89.60
Purchase #5	$147.55	13.586%	$167.5961	$167.60	$167.60	$167.60
Purchase #6	$171.65	8.332%	$185.9519	$185.95	$185.95	$186.00
Purchase #7	$41.34	5.543%	$43.6315	$43.63	$43.65	$43.60
7 purchase totals =	$869.89		$962.5200	$962.52	$962.55	$962.50