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	$168.34	10.193%	$185.4989	$185.50	$185.50	$185.50
Purchase #2	$172.54	5.446%	$181.9365	$181.94	$181.95	$181.90
Purchase #3	$171.66	7.778%	$185.0117	$185.01	$185.00	$185.00
Purchase #4	$224.45	3.141%	$231.5	$231.50	$231.50	$231.50
Purchase #5	$128.59	4.534%	$134.4203	$134.42	$134.40	$134.40
Purchase #6	$175.33	9.411%	$191.8303	$191.83	$191.85	$191.80
Purchase #7	$13.90	4.242%	$14.4896	$14.49	$14.50	$14.50
7 purchase totals =	$1,054.81		$1,124.6873	$1,124.69	$1,124.70	$1,124.60