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	$10.91	7.638%	$11.7433	$11.74	$11.75	$11.70
Purchase #2	$176.97	12.709%	$199.4611	$199.46	$199.45	$199.50
Purchase #3	$38.78	13.721%	$44.101	$44.10	$44.10	$44.10
Purchase #4	$95.66	8.688%	$103.9709	$103.97	$103.95	$104.00
Purchase #5	$93.50	6.578%	$99.6504	$99.65	$99.65	$99.70
Purchase #6	$193.90	8.462%	$210.3078	$210.31	$210.30	$210.30
Purchase #7	$187.78	4.540%	$196.3052	$196.31	$196.30	$196.30
7 purchase totals =	$797.50		$865.5397	$865.54	$865.50	$865.60