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	$139.32	7.707%	$150.0574	$150.06	$150.05	$150.10
Purchase #2	$10.93	7.456%	$11.7449	$11.74	$11.75	$11.70
Purchase #3	$104.26	5.287%	$109.7722	$109.77	$109.75	$109.80
Purchase #4	$121.55	5.678%	$128.4516	$128.45	$128.45	$128.50
Purchase #5	$144.76	13.536%	$164.3547	$164.35	$164.35	$164.40
Purchase #6	$99.53	5.664%	$105.1674	$105.17	$105.15	$105.20
Purchase #7	$215.27	9.831%	$236.4332	$236.43	$236.45	$236.40
7 purchase totals =	$835.62		$905.9814	$905.97	$905.95	$906.10