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	$63.60	4.427%	$66.4156	$66.42	$66.40	$66.40
Purchase #2	$187.41	6.837%	$200.2232	$200.22	$200.20	$200.20
Purchase #3	$7.63	7.735%	$8.2202	$8.22	$8.20	$8.20
Purchase #4	$152.40	13.224%	$172.5534	$172.55	$172.55	$172.60
Purchase #5	$146.28	4.155%	$152.3579	$152.36	$152.35	$152.40
Purchase #6	$241.85	13.239%	$273.8685	$273.87	$273.85	$273.90
Purchase #7	$200.84	6.266%	$213.4246	$213.42	$213.40	$213.40
7 purchase totals =	$1,000.01		$1,087.0634	$1,087.06	$1,086.95	$1,087.10