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	$65.58	10.383%	$72.3892	$72.39	$72.40	$72.40
Purchase #2	$215.31	9.425%	$235.603	$235.60	$235.60	$235.60
Purchase #3	$192.89	8.533%	$209.3493	$209.35	$209.35	$209.30
Purchase #4	$182.99	7.436%	$196.5971	$196.60	$196.60	$196.60
Purchase #5	$183.46	12.865%	$207.0621	$207.06	$207.05	$207.10
Purchase #6	$29.32	3.798%	$30.4336	$30.43	$30.45	$30.40
Purchase #7	$46.28	11.395%	$51.5536	$51.55	$51.55	$51.60
7 purchase totals =	$915.83		$1,002.9879	$1,002.98	$1,003.00	$1,003.00