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	$59.33	5.299%	$62.4739	$62.47	$62.45	$62.50
Purchase #2	$103.69	9.429%	$113.4669	$113.47	$113.45	$113.50
Purchase #3	$156.96	10.777%	$173.8756	$173.88	$173.90	$173.90
Purchase #4	$168.39	4.658%	$176.2336	$176.23	$176.25	$176.20
Purchase #5	$163.42	10.200%	$180.0888	$180.09	$180.10	$180.10
Purchase #6	$126.45	8.166%	$136.7759	$136.78	$136.80	$136.80
Purchase #7	$29.27	11.218%	$32.5535	$32.55	$32.55	$32.60
7 purchase totals =	$807.51		$875.4682	$875.47	$875.50	$875.60