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	$43.59	11.765%	$48.7184	$48.72	$48.70	$48.70
Purchase #2	$50.30	13.121%	$56.8999	$56.90	$56.90	$56.90
Purchase #3	$45.71	6.102%	$48.4992	$48.50	$48.50	$48.50
Purchase #4	$234.79	10.680%	$259.8656	$259.87	$259.85	$259.90
Purchase #5	$38.98	3.482%	$40.3373	$40.34	$40.35	$40.30
Purchase #6	$222.33	3.647%	$230.4384	$230.44	$230.45	$230.40
Purchase #7	$28.43	13.587%	$32.2928	$32.29	$32.30	$32.30
7 purchase totals =	$664.13		$717.0516	$717.06	$717.05	$717.00