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	$62.82	12.405%	$70.6128	$70.61	$70.60	$70.60
Purchase #2	$112.60	6.520%	$119.9415	$119.94	$119.95	$119.90
Purchase #3	$109.54	13.179%	$123.9763	$123.98	$124.00	$124.00
Purchase #4	$225.38	10.431%	$248.8894	$248.89	$248.90	$248.90
Purchase #5	$132.64	5.275%	$139.6368	$139.64	$139.65	$139.60
Purchase #6	$248.36	6.705%	$265.0125	$265.01	$265.00	$265.00
Purchase #7	$42.40	10.556%	$46.8757	$46.88	$46.90	$46.90
7 purchase totals =	$933.74		$1,014.9450	$1,014.95	$1,015.00	$1,014.90