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	$99.65	10.209%	$109.8233	$109.82	$109.80	$109.80
Purchase #2	$66.64	8.587%	$72.3624	$72.36	$72.35	$72.40
Purchase #3	$114.39	4.365%	$119.3831	$119.38	$119.40	$119.40
Purchase #4	$40.72	10.723%	$45.0864	$45.09	$45.10	$45.10
Purchase #5	$34.39	12.117%	$38.557	$38.56	$38.55	$38.60
Purchase #6	$121.99	10.506%	$134.8063	$134.81	$134.80	$134.80
Purchase #7	$42.50	10.611%	$47.0097	$47.01	$47.00	$47.00
7 purchase totals =	$520.28		$567.0282	$567.03	$567.00	$567.10