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	$132.81	5.318%	$139.8728	$139.87	$139.85	$139.90
Purchase #2	$72.42	5.609%	$76.482	$76.48	$76.50	$76.50
Purchase #3	$210.78	10.544%	$233.0046	$233.00	$233.00	$233.00
Purchase #4	$18.69	10.174%	$20.5915	$20.59	$20.60	$20.60
Purchase #5	$95.25	3.297%	$98.3904	$98.39	$98.40	$98.40
Purchase #6	$188.51	13.739%	$214.4094	$214.41	$214.40	$214.40
Purchase #7	$133.71	3.134%	$137.9005	$137.90	$137.90	$137.90
7 purchase totals =	$852.17		$920.6512	$920.64	$920.65	$920.70