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	$108.50	13.722%	$123.3884	$123.39	$123.40	$123.40
Purchase #2	$39.59	11.371%	$44.0918	$44.09	$44.10	$44.10
Purchase #3	$56.50	4.539%	$59.0645	$59.06	$59.05	$59.10
Purchase #4	$143.39	5.657%	$151.5016	$151.50	$151.50	$151.50
Purchase #5	$74.61	9.128%	$81.4204	$81.42	$81.40	$81.40
Purchase #6	$171.78	8.436%	$186.2714	$186.27	$186.25	$186.30
Purchase #7	$63.27	6.336%	$67.2788	$67.28	$67.30	$67.30
7 purchase totals =	$657.64		$713.0169	$713.01	$713.00	$713.10