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	$17.83	9.708%	$19.5609	$19.56	$19.55	$19.60
Purchase #2	$54.87	4.836%	$57.5235	$57.52	$57.50	$57.50
Purchase #3	$63.52	4.772%	$66.5512	$66.55	$66.55	$66.60
Purchase #4	$174.86	4.529%	$182.7794	$182.78	$182.80	$182.80
Purchase #5	$35.78	5.871%	$37.8806	$37.88	$37.90	$37.90
Purchase #6	$159.87	5.368%	$168.4518	$168.45	$168.45	$168.50
Purchase #7	$72.43	12.574%	$81.5373	$81.54	$81.55	$81.50
7 purchase totals =	$579.16		$614.2847	$614.28	$614.30	$614.40