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	$142.64	7.509%	$153.3508	$153.35	$153.35	$153.40
Purchase #2	$57.38	3.369%	$59.3131	$59.31	$59.30	$59.30
Purchase #3	$144.58	6.413%	$153.8519	$153.85	$153.85	$153.90
Purchase #4	$172.71	3.507%	$178.7669	$178.77	$178.75	$178.80
Purchase #5	$150.42	11.312%	$167.4355	$167.44	$167.45	$167.40
Purchase #6	$92.31	8.664%	$100.3077	$100.31	$100.30	$100.30
Purchase #7	$187.91	4.733%	$196.8038	$196.80	$196.80	$196.80
7 purchase totals =	$947.95		$1,009.8297	$1,009.83	$1,009.80	$1,009.90