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	$158.45	3.805%	$164.479	$164.48	$164.50	$164.50
Purchase #2	$49.27	10.174%	$54.2827	$54.28	$54.30	$54.30
Purchase #3	$93.64	11.509%	$104.417	$104.42	$104.40	$104.40
Purchase #4	$95.95	8.347%	$103.9589	$103.96	$103.95	$104.00
Purchase #5	$217.27	11.568%	$242.4038	$242.40	$242.40	$242.40
Purchase #6	$95.73	10.475%	$105.7577	$105.76	$105.75	$105.80
Purchase #7	$118.78	3.661%	$123.1285	$123.13	$123.15	$123.10
7 purchase totals =	$829.09		$898.4276	$898.43	$898.45	$898.50