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	$117.25	9.643%	$128.5564	$128.56	$128.55	$128.60
Purchase #2	$180.42	11.193%	$200.6144	$200.61	$200.60	$200.60
Purchase #3	$230.59	7.698%	$248.3408	$248.34	$248.35	$248.30
Purchase #4	$56.79	11.320%	$63.2186	$63.22	$63.20	$63.20
Purchase #5	$17.39	12.457%	$19.5563	$19.56	$19.55	$19.60
Purchase #6	$35.82	11.357%	$39.8881	$39.89	$39.90	$39.90
Purchase #7	$96.59	8.772%	$105.0629	$105.06	$105.05	$105.10
7 purchase totals =	$734.85		$805.2375	$805.24	$805.20	$805.30