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	$213.63	8.262%	$231.2801	$231.28	$231.30	$231.30
Purchase #2	$51.28	3.631%	$53.142	$53.14	$53.15	$53.10
Purchase #3	$35.74	10.315%	$39.4266	$39.43	$39.45	$39.40
Purchase #4	$71.71	8.125%	$77.5364	$77.54	$77.55	$77.50
Purchase #5	$109.89	8.720%	$119.4724	$119.47	$119.45	$119.50
Purchase #6	$205.54	13.610%	$233.514	$233.51	$233.50	$233.50
Purchase #7	$28.28	5.309%	$29.7814	$29.78	$29.80	$29.80
7 purchase totals =	$716.07		$784.1529	$784.15	$784.20	$784.10