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	$170.45	6.825%	$182.0832	$182.08	$182.10	$182.10
Purchase #2	$128.94	11.558%	$143.8429	$143.84	$143.85	$143.80
Purchase #3	$127.44	3.564%	$131.982	$131.98	$132.00	$132.00
Purchase #4	$59.84	10.123%	$65.8976	$65.90	$65.90	$65.90
Purchase #5	$81.60	4.366%	$85.1627	$85.16	$85.15	$85.20
Purchase #6	$235.92	8.144%	$255.1333	$255.13	$255.15	$255.10
Purchase #7	$62.87	7.646%	$67.677	$67.68	$67.70	$67.70
7 purchase totals =	$867.06		$931.7787	$931.77	$931.85	$931.80