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	$104.55	11.630%	$116.7092	$116.71	$116.70	$116.70
Purchase #2	$70.90	9.225%	$77.4405	$77.44	$77.45	$77.40
Purchase #3	$43.88	13.797%	$49.9341	$49.93	$49.95	$49.90
Purchase #4	$55.77	12.252%	$62.6029	$62.60	$62.60	$62.60
Purchase #5	$51.39	12.644%	$57.8878	$57.89	$57.90	$57.90
Purchase #6	$191.56	12.451%	$215.4111	$215.41	$215.40	$215.40
Purchase #7	$111.26	7.840%	$119.9828	$119.98	$120.00	$120.00
7 purchase totals =	$629.31		$699.9684	$699.96	$700.00	$699.90