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	$175.98	8.444%	$190.8398	$190.84	$190.85	$190.80
Purchase #2	$160.46	10.590%	$177.4527	$177.45	$177.45	$177.50
Purchase #3	$165.95	13.809%	$188.866	$188.87	$188.85	$188.90
Purchase #4	$53.32	10.553%	$58.9469	$58.95	$58.95	$58.90
Purchase #5	$41.85	13.342%	$47.4336	$47.43	$47.45	$47.40
Purchase #6	$191.52	12.469%	$215.4006	$215.40	$215.40	$215.40
Purchase #7	$114.34	6.354%	$121.6052	$121.61	$121.60	$121.60
7 purchase totals =	$903.42		$1,000.5448	$1,000.55	$1,000.55	$1,000.50