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	$218.90	13.619%	$248.712	$248.71	$248.70	$248.70
Purchase #2	$165.40	4.269%	$172.4609	$172.46	$172.45	$172.50
Purchase #3	$124.42	10.530%	$137.5214	$137.52	$137.50	$137.50
Purchase #4	$24.33	11.296%	$27.0783	$27.08	$27.10	$27.10
Purchase #5	$142.72	10.834%	$158.1823	$158.18	$158.20	$158.20
Purchase #6	$147.52	7.364%	$158.3834	$158.38	$158.40	$158.40
Purchase #7	$56.60	11.629%	$63.182	$63.18	$63.20	$63.20
7 purchase totals =	$879.89		$965.5203	$965.51	$965.55	$965.60