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	$155.79	8.119%	$168.4386	$168.44	$168.45	$168.40
Purchase #2	$90.56	9.469%	$99.1351	$99.14	$99.15	$99.10
Purchase #3	$212.95	9.592%	$233.3762	$233.38	$233.40	$233.40
Purchase #4	$80.69	11.223%	$89.7458	$89.75	$89.75	$89.70
Purchase #5	$26.59	9.791%	$29.1934	$29.19	$29.20	$29.20
Purchase #6	$81.70	7.256%	$87.6282	$87.63	$87.65	$87.60
Purchase #7	$51.72	5.434%	$54.5305	$54.53	$54.55	$54.50
7 purchase totals =	$700.00		$762.0478	$762.06	$762.15	$761.90