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	$55.98	5.806%	$59.2302	$59.23	$59.25	$59.20
Purchase #2	$35.47	7.577%	$38.1576	$38.16	$38.15	$38.20
Purchase #3	$29.50	13.310%	$33.4265	$33.43	$33.45	$33.40
Purchase #4	$25.61	10.850%	$28.3887	$28.39	$28.40	$28.40
Purchase #5	$168.42	8.558%	$182.8334	$182.83	$182.85	$182.80
Purchase #6	$194.93	6.866%	$208.3139	$208.31	$208.30	$208.30
Purchase #7	$159.80	10.438%	$176.4799	$176.48	$176.50	$176.50
7 purchase totals =	$669.71		$726.8302	$726.83	$726.90	$726.80