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	$209.55	6.593%	$223.3656	$223.37	$223.35	$223.40
Purchase #2	$113.39	3.661%	$117.5412	$117.54	$117.55	$117.50
Purchase #3	$37.65	6.745%	$40.1895	$40.19	$40.20	$40.20
Purchase #4	$136.60	5.695%	$144.3794	$144.38	$144.40	$144.40
Purchase #5	$33.67	10.155%	$37.0892	$37.09	$37.10	$37.10
Purchase #6	$247.61	7.212%	$265.4676	$265.47	$265.45	$265.50
Purchase #7	$117.43	12.459%	$132.0606	$132.06	$132.05	$132.10
7 purchase totals =	$895.90		$960.0931	$960.10	$960.10	$960.20