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	$241.29	10.461%	$266.5313	$266.53	$266.55	$266.50
Purchase #2	$40.49	10.410%	$44.705	$44.71	$44.70	$44.70
Purchase #3	$72.66	6.320%	$77.2521	$77.25	$77.25	$77.30
Purchase #4	$55.34	3.582%	$57.3223	$57.32	$57.30	$57.30
Purchase #5	$73.72	6.744%	$78.6917	$78.69	$78.70	$78.70
Purchase #6	$156.75	8.371%	$169.8715	$169.87	$169.85	$169.90
Purchase #7	$245.52	11.227%	$273.0845	$273.08	$273.10	$273.10
7 purchase totals =	$885.77		$967.4584	$967.45	$967.45	$967.50