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	$173.28	4.330%	$180.783	$180.78	$180.80	$180.80
Purchase #2	$240.71	6.562%	$256.5054	$256.51	$256.50	$256.50
Purchase #3	$12.77	8.761%	$13.8888	$13.89	$13.90	$13.90
Purchase #4	$239.66	10.392%	$264.5655	$264.57	$264.55	$264.60
Purchase #5	$132.66	5.492%	$139.9457	$139.95	$139.95	$139.90
Purchase #6	$169.45	4.368%	$176.8516	$176.85	$176.85	$176.90
Purchase #7	$62.47	4.739%	$65.4305	$65.43	$65.45	$65.40
7 purchase totals =	$1,031.00		$1,097.9705	$1,097.98	$1,098.00	$1,098.00