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	$44.32	3.522%	$45.881	$45.88	$45.90	$45.90
Purchase #2	$127.72	13.482%	$144.9392	$144.94	$144.95	$144.90
Purchase #3	$149.28	9.765%	$163.8572	$163.86	$163.85	$163.90
Purchase #4	$46.53	3.815%	$48.3051	$48.31	$48.30	$48.30
Purchase #5	$18.32	7.701%	$19.7308	$19.73	$19.75	$19.70
Purchase #6	$174.78	13.413%	$198.2232	$198.22	$198.20	$198.20
Purchase #7	$55.30	11.482%	$61.6495	$61.65	$61.65	$61.60
7 purchase totals =	$616.25		$682.5860	$682.59	$682.60	$682.50