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	$60.83	4.509%	$63.5728	$63.57	$63.55	$63.60
Purchase #2	$101.95	3.160%	$105.1716	$105.17	$105.15	$105.20
Purchase #3	$130.25	13.638%	$148.0135	$148.01	$148.00	$148.00
Purchase #4	$13.36	3.215%	$13.7895	$13.79	$13.80	$13.80
Purchase #5	$71.50	9.608%	$78.3697	$78.37	$78.35	$78.40
Purchase #6	$84.52	11.550%	$94.2821	$94.28	$94.30	$94.30
Purchase #7	$45.82	13.437%	$51.9768	$51.98	$52.00	$52.00
7 purchase totals =	$508.23		$555.1760	$555.17	$555.15	$555.30