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	$85.83	4.405%	$89.6108	$89.61	$89.60	$89.60
Purchase #2	$5.69	3.735%	$5.9025	$5.90	$5.90	$5.90
Purchase #3	$215.27	5.476%	$227.0582	$227.06	$227.05	$227.10
Purchase #4	$46.37	10.634%	$51.301	$51.30	$51.30	$51.30
Purchase #5	$123.95	13.561%	$140.7589	$140.76	$140.75	$140.80
Purchase #6	$10.39	4.274%	$10.8341	$10.83	$10.85	$10.80
Purchase #7	$119.42	11.253%	$132.8583	$132.86	$132.85	$132.90
7 purchase totals =	$606.92		$658.3238	$658.32	$658.30	$658.40