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	$192.80	8.362%	$208.9219	$208.92	$208.90	$208.90
Purchase #2	$124.38	10.508%	$137.4499	$137.45	$137.45	$137.40
Purchase #3	$223.81	4.798%	$234.5484	$234.55	$234.55	$234.50
Purchase #4	$132.80	5.738%	$140.4201	$140.42	$140.40	$140.40
Purchase #5	$104.50	6.603%	$111.4001	$111.40	$111.40	$111.40
Purchase #6	$133.81	3.245%	$138.1521	$138.15	$138.15	$138.20
Purchase #7	$219.72	8.123%	$237.5679	$237.57	$237.55	$237.60
7 purchase totals =	$1,131.82		$1,208.4604	$1,208.46	$1,208.40	$1,208.40