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	$224.80	13.632%	$255.4447	$255.44	$255.45	$255.40
Purchase #2	$115.27	3.105%	$118.8491	$118.85	$118.85	$118.80
Purchase #3	$185.72	13.534%	$210.8553	$210.86	$210.85	$210.90
Purchase #4	$141.69	7.667%	$152.5534	$152.55	$152.55	$152.60
Purchase #5	$8.84	8.631%	$9.603	$9.60	$9.60	$9.60
Purchase #6	$234.89	3.166%	$242.3266	$242.33	$242.35	$242.30
Purchase #7	$53.34	13.239%	$60.4017	$60.40	$60.40	$60.40
7 purchase totals =	$964.55		$1,050.0338	$1,050.03	$1,050.05	$1,050.00