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	$143.65	10.432%	$158.6356	$158.64	$158.65	$158.60
Purchase #2	$104.45	12.550%	$117.5585	$117.56	$117.55	$117.60
Purchase #3	$72.61	8.235%	$78.5894	$78.59	$78.60	$78.60
Purchase #4	$180.66	13.167%	$204.4475	$204.45	$204.45	$204.40
Purchase #5	$88.83	7.547%	$95.534	$95.53	$95.55	$95.50
Purchase #6	$50.55	7.171%	$54.1749	$54.17	$54.15	$54.20
Purchase #7	$48.65	5.224%	$51.1915	$51.19	$51.20	$51.20
7 purchase totals =	$689.40		$760.1314	$760.13	$760.15	$760.10