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	$55.25	8.174%	$59.7661	$59.77	$59.75	$59.80
Purchase #2	$97.60	12.392%	$109.6946	$109.69	$109.70	$109.70
Purchase #3	$25.28	9.396%	$27.6553	$27.66	$27.65	$27.70
Purchase #4	$202.37	10.103%	$222.8154	$222.82	$222.80	$222.80
Purchase #5	$179.98	12.301%	$202.1193	$202.12	$202.10	$202.10
Purchase #6	$119.57	5.754%	$126.4501	$126.45	$126.45	$126.50
Purchase #7	$95.81	10.573%	$105.94	$105.94	$105.95	$105.90
7 purchase totals =	$775.86		$854.4408	$854.45	$854.40	$854.50