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	$59.49	11.605%	$66.3938	$66.39	$66.40	$66.40
Purchase #2	$185.89	11.583%	$207.4216	$207.42	$207.40	$207.40
Purchase #3	$137.83	10.346%	$152.0899	$152.09	$152.10	$152.10
Purchase #4	$170.90	4.623%	$178.8007	$178.80	$178.80	$178.80
Purchase #5	$200.31	5.739%	$211.8058	$211.81	$211.80	$211.80
Purchase #6	$47.52	8.376%	$51.5003	$51.50	$51.50	$51.50
Purchase #7	$217.90	12.396%	$244.9109	$244.91	$244.90	$244.90
7 purchase totals =	$1,019.84		$1,112.9230	$1,112.92	$1,112.90	$1,112.90