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	$212.66	6.789%	$227.0975	$227.10	$227.10	$227.10
Purchase #2	$30.34	9.757%	$33.3003	$33.30	$33.30	$33.30
Purchase #3	$230.66	12.198%	$258.7959	$258.80	$258.80	$258.80
Purchase #4	$118.90	11.378%	$132.4284	$132.43	$132.45	$132.40
Purchase #5	$20.82	4.857%	$21.8312	$21.83	$21.85	$21.80
Purchase #6	$162.92	3.265%	$168.2393	$168.24	$168.25	$168.20
Purchase #7	$228.32	12.355%	$256.5289	$256.53	$256.55	$256.50
7 purchase totals =	$1,004.62		$1,098.2215	$1,098.23	$1,098.30	$1,098.10