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	$238.34	7.822%	$256.983	$256.98	$257.00	$257.00
Purchase #2	$69.56	4.346%	$72.5831	$72.58	$72.60	$72.60
Purchase #3	$145.95	6.606%	$155.5915	$155.59	$155.60	$155.60
Purchase #4	$138.54	5.598%	$146.2955	$146.30	$146.30	$146.30
Purchase #5	$94.78	6.510%	$100.9502	$100.95	$100.95	$101.00
Purchase #6	$189.51	11.308%	$210.9398	$210.94	$210.95	$210.90
Purchase #7	$202.49	9.789%	$222.3117	$222.31	$222.30	$222.30
7 purchase totals =	$1,079.17		$1,165.6548	$1,165.65	$1,165.70	$1,165.70