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	$108.90	5.858%	$115.2794	$115.28	$115.30	$115.30
Purchase #2	$48.59	6.596%	$51.795	$51.80	$51.80	$51.80
Purchase #3	$61.53	4.551%	$64.3302	$64.33	$64.35	$64.30
Purchase #4	$94.88	5.278%	$99.8878	$99.89	$99.90	$99.90
Purchase #5	$141.91	9.851%	$155.8896	$155.89	$155.90	$155.90
Purchase #6	$114.54	10.421%	$126.4762	$126.48	$126.50	$126.50
Purchase #7	$85.80	11.164%	$95.3787	$95.38	$95.40	$95.40
7 purchase totals =	$656.15		$709.0369	$709.05	$709.15	$709.10