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	$128.28	10.818%	$142.1573	$142.16	$142.15	$142.20
Purchase #2	$92.32	12.111%	$103.5009	$103.50	$103.50	$103.50
Purchase #3	$39.37	5.814%	$41.659	$41.66	$41.65	$41.70
Purchase #4	$140.88	3.341%	$145.5868	$145.59	$145.60	$145.60
Purchase #5	$47.86	9.699%	$52.5019	$52.50	$52.50	$52.50
Purchase #6	$24.62	3.649%	$25.5184	$25.52	$25.50	$25.50
Purchase #7	$50.45	12.706%	$56.8602	$56.86	$56.85	$56.90
7 purchase totals =	$523.78		$567.7845	$567.79	$567.75	$567.90