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	$248.27	9.771%	$272.5285	$272.53	$272.55	$272.50
Purchase #2	$165.39	6.326%	$175.8526	$175.85	$175.85	$175.90
Purchase #3	$56.87	4.167%	$59.2398	$59.24	$59.25	$59.20
Purchase #4	$139.61	8.654%	$151.6918	$151.69	$151.70	$151.70
Purchase #5	$238.93	13.583%	$271.3839	$271.38	$271.40	$271.40
Purchase #6	$120.39	6.723%	$128.4838	$128.48	$128.50	$128.50
Purchase #7	$147.86	4.687%	$154.7902	$154.79	$154.80	$154.80
7 purchase totals =	$1,117.32		$1,213.9706	$1,213.96	$1,214.05	$1,214.00