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	$178.78	4.328%	$186.5176	$186.52	$186.50	$186.50
Purchase #2	$43.35	10.339%	$47.832	$47.83	$47.85	$47.80
Purchase #3	$126.83	12.659%	$142.8854	$142.89	$142.90	$142.90
Purchase #4	$206.74	5.303%	$217.7034	$217.70	$217.70	$217.70
Purchase #5	$129.69	13.617%	$147.3499	$147.35	$147.35	$147.30
Purchase #6	$224.88	3.389%	$232.5012	$232.50	$232.50	$232.50
Purchase #7	$73.78	9.102%	$80.4955	$80.50	$80.50	$80.50
7 purchase totals =	$984.05		$1,055.2850	$1,055.29	$1,055.30	$1,055.20