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	$70.84	10.420%	$78.2215	$78.22	$78.20	$78.20
Purchase #2	$212.77	12.227%	$238.7854	$238.79	$238.80	$238.80
Purchase #3	$131.83	4.379%	$137.6028	$137.60	$137.60	$137.60
Purchase #4	$194.48	7.216%	$208.5137	$208.51	$208.50	$208.50
Purchase #5	$31.94	5.286%	$33.6283	$33.63	$33.65	$33.60
Purchase #6	$242.45	5.628%	$256.0951	$256.10	$256.10	$256.10
Purchase #7	$92.46	11.378%	$102.9801	$102.98	$103.00	$103.00
7 purchase totals =	$976.77		$1,055.8269	$1,055.83	$1,055.85	$1,055.80