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	$239.56	10.867%	$265.593	$265.59	$265.60	$265.60
Purchase #2	$109.83	4.206%	$114.4494	$114.45	$114.45	$114.40
Purchase #3	$194.78	9.379%	$213.0484	$213.05	$213.05	$213.00
Purchase #4	$37.66	7.373%	$40.4367	$40.44	$40.45	$40.40
Purchase #5	$136.25	10.326%	$150.3192	$150.32	$150.30	$150.30
Purchase #6	$162.39	11.259%	$180.6735	$180.67	$180.65	$180.70
Purchase #7	$164.37	13.328%	$186.2772	$186.28	$186.30	$186.30
7 purchase totals =	$1,044.84		$1,150.7974	$1,150.80	$1,150.80	$1,150.70