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	$161.46	6.389%	$171.7757	$171.78	$171.80	$171.80
Purchase #2	$13.38	6.292%	$14.2219	$14.22	$14.20	$14.20
Purchase #3	$156.55	4.826%	$164.1051	$164.11	$164.10	$164.10
Purchase #4	$133.76	5.330%	$140.8894	$140.89	$140.90	$140.90
Purchase #5	$215.53	5.739%	$227.8993	$227.90	$227.90	$227.90
Purchase #6	$151.61	10.852%	$168.0627	$168.06	$168.05	$168.10
Purchase #7	$176.80	7.261%	$189.6374	$189.64	$189.65	$189.60
7 purchase totals =	$1,009.09		$1,076.5915	$1,076.60	$1,076.60	$1,076.60