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	$186.83	5.212%	$196.5676	$196.57	$196.55	$196.60
Purchase #2	$81.32	7.583%	$87.4865	$87.49	$87.50	$87.50
Purchase #3	$48.81	3.411%	$50.4749	$50.47	$50.45	$50.50
Purchase #4	$95.56	8.775%	$103.9454	$103.95	$103.95	$103.90
Purchase #5	$194.76	4.553%	$203.6274	$203.63	$203.65	$203.60
Purchase #6	$186.91	12.622%	$210.5018	$210.50	$210.50	$210.50
Purchase #7	$186.61	9.528%	$204.3902	$204.39	$204.40	$204.40
7 purchase totals =	$980.80		$1,056.9938	$1,057.00	$1,057.00	$1,057.00