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	$53.39	13.413%	$60.5512	$60.55	$60.55	$60.60
Purchase #2	$131.48	8.195%	$142.2548	$142.25	$142.25	$142.30
Purchase #3	$217.46	11.565%	$242.6092	$242.61	$242.60	$242.60
Purchase #4	$156.49	7.541%	$168.2909	$168.29	$168.30	$168.30
Purchase #5	$192.59	5.659%	$203.4887	$203.49	$203.50	$203.50
Purchase #6	$205.92	4.737%	$215.6744	$215.67	$215.65	$215.70
Purchase #7	$156.87	6.129%	$166.4846	$166.48	$166.50	$166.50
7 purchase totals =	$1,114.20		$1,199.3538	$1,199.34	$1,199.35	$1,199.50