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	$168.88	8.276%	$182.8565	$182.86	$182.85	$182.90
Purchase #2	$123.61	6.772%	$131.9809	$131.98	$132.00	$132.00
Purchase #3	$226.98	6.511%	$241.7587	$241.76	$241.75	$241.80
Purchase #4	$83.84	7.848%	$90.4198	$90.42	$90.40	$90.40
Purchase #5	$168.49	6.109%	$178.7831	$178.78	$178.80	$178.80
Purchase #6	$150.74	13.698%	$171.3884	$171.39	$171.40	$171.40
Purchase #7	$78.98	7.859%	$85.187	$85.19	$85.20	$85.20
7 purchase totals =	$1,001.52		$1,082.3744	$1,082.38	$1,082.40	$1,082.50