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	$108.59	8.536%	$117.8592	$117.86	$117.85	$117.90
Purchase #2	$79.96	7.679%	$86.1001	$86.10	$86.10	$86.10
Purchase #3	$89.75	11.333%	$99.9214	$99.92	$99.90	$99.90
Purchase #4	$58.82	7.551%	$63.2615	$63.26	$63.25	$63.30
Purchase #5	$244.55	4.732%	$256.1221	$256.12	$256.10	$256.10
Purchase #6	$178.78	11.129%	$198.6764	$198.68	$198.70	$198.70
Purchase #7	$246.54	6.618%	$262.856	$262.86	$262.85	$262.90
7 purchase totals =	$1,006.99		$1,084.7967	$1,084.80	$1,084.75	$1,084.90