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	$145.51	8.646%	$158.0908	$158.09	$158.10	$158.10
Purchase #2	$155.30	12.247%	$174.3196	$174.32	$174.30	$174.30
Purchase #3	$217.51	8.639%	$236.3007	$236.30	$236.30	$236.30
Purchase #4	$7.36	6.403%	$7.8313	$7.83	$7.85	$7.80
Purchase #5	$29.81	8.246%	$32.2681	$32.27	$32.25	$32.30
Purchase #6	$67.32	6.726%	$71.8479	$71.85	$71.85	$71.80
Purchase #7	$34.95	8.147%	$37.7974	$37.80	$37.80	$37.80
7 purchase totals =	$657.76		$718.4558	$718.46	$718.45	$718.40