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	$84.58	6.216%	$89.8375	$89.84	$89.85	$89.80
Purchase #2	$69.82	3.794%	$72.469	$72.47	$72.45	$72.50
Purchase #3	$222.78	8.772%	$242.3223	$242.32	$242.30	$242.30
Purchase #4	$70.91	10.504%	$78.3584	$78.36	$78.35	$78.40
Purchase #5	$183.64	12.143%	$205.9394	$205.94	$205.95	$205.90
Purchase #6	$237.86	9.498%	$260.4519	$260.45	$260.45	$260.50
Purchase #7	$32.52	8.868%	$35.4039	$35.40	$35.40	$35.40
7 purchase totals =	$902.11		$984.7824	$984.78	$984.75	$984.80