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	$174.38	10.141%	$192.0639	$192.06	$192.05	$192.10
Purchase #2	$16.94	8.563%	$18.3906	$18.39	$18.40	$18.40
Purchase #3	$132.55	8.256%	$143.4933	$143.49	$143.50	$143.50
Purchase #4	$75.78	4.178%	$78.9461	$78.95	$78.95	$78.90
Purchase #5	$195.25	10.507%	$215.7649	$215.76	$215.75	$215.80
Purchase #6	$236.27	10.650%	$261.4328	$261.43	$261.45	$261.40
Purchase #7	$183.85	4.361%	$191.8677	$191.87	$191.85	$191.90
7 purchase totals =	$1,015.02		$1,101.9593	$1,101.95	$1,101.95	$1,102.00