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	$190.91	9.762%	$209.5466	$209.55	$209.55	$209.50
Purchase #2	$142.85	7.823%	$154.0252	$154.03	$154.05	$154.00
Purchase #3	$138.58	10.355%	$152.93	$152.93	$152.95	$152.90
Purchase #4	$37.32	4.217%	$38.8938	$38.89	$38.90	$38.90
Purchase #5	$166.69	10.310%	$183.8757	$183.88	$183.90	$183.90
Purchase #6	$116.55	8.576%	$126.5453	$126.55	$126.55	$126.50
Purchase #7	$236.95	10.686%	$262.2705	$262.27	$262.25	$262.30
7 purchase totals =	$1,029.85		$1,128.0871	$1,128.10	$1,128.15	$1,128.00