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	$62.86	4.330%	$65.5818	$65.58	$65.60	$65.60
Purchase #2	$43.89	7.833%	$47.3279	$47.33	$47.35	$47.30
Purchase #3	$10.51	6.166%	$11.158	$11.16	$11.15	$11.20
Purchase #4	$20.97	6.722%	$22.3796	$22.38	$22.40	$22.40
Purchase #5	$166.88	10.595%	$184.5609	$184.56	$184.55	$184.60
Purchase #6	$246.74	3.521%	$255.4277	$255.43	$255.45	$255.40
Purchase #7	$41.38	12.538%	$46.5682	$46.57	$46.55	$46.60
7 purchase totals =	$593.23		$633.0041	$633.01	$633.05	$633.10