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	$116.85	9.791%	$128.2908	$128.29	$128.30	$128.30
Purchase #2	$31.39	7.713%	$33.8111	$33.81	$33.80	$33.80
Purchase #3	$48.72	5.201%	$51.2539	$51.25	$51.25	$51.30
Purchase #4	$55.81	5.757%	$59.023	$59.02	$59.00	$59.00
Purchase #5	$84.50	12.740%	$95.2653	$95.27	$95.25	$95.30
Purchase #6	$19.85	3.503%	$20.5453	$20.55	$20.55	$20.50
Purchase #7	$74.96	7.426%	$80.5265	$80.53	$80.55	$80.50
7 purchase totals =	$432.08		$468.7159	$468.72	$468.70	$468.70