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	$213.80	8.733%	$232.4712	$232.47	$232.45	$232.50
Purchase #2	$77.55	9.757%	$85.1166	$85.12	$85.10	$85.10
Purchase #3	$74.31	8.262%	$80.4495	$80.45	$80.45	$80.40
Purchase #4	$141.72	7.841%	$152.8323	$152.83	$152.85	$152.80
Purchase #5	$164.33	9.281%	$179.5815	$179.58	$179.60	$179.60
Purchase #6	$241.59	6.564%	$257.448	$257.45	$257.45	$257.40
Purchase #7	$174.29	5.788%	$184.3779	$184.38	$184.40	$184.40
7 purchase totals =	$1,087.59		$1,172.2770	$1,172.28	$1,172.30	$1,172.20