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	$139.88	8.870%	$152.2874	$152.29	$152.30	$152.30
Purchase #2	$124.63	7.397%	$133.8489	$133.85	$133.85	$133.80
Purchase #3	$150.89	4.645%	$157.8988	$157.90	$157.90	$157.90
Purchase #4	$220.71	13.679%	$250.9009	$250.90	$250.90	$250.90
Purchase #5	$38.96	3.147%	$40.1861	$40.19	$40.20	$40.20
Purchase #6	$60.51	9.528%	$66.2754	$66.28	$66.30	$66.30
Purchase #7	$154.31	5.403%	$162.6474	$162.65	$162.65	$162.60
7 purchase totals =	$889.89		$964.0449	$964.06	$964.10	$964.00