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	$208.63	9.847%	$229.1738	$229.17	$229.15	$229.20
Purchase #2	$178.57	3.613%	$185.0217	$185.02	$185.00	$185.00
Purchase #3	$243.70	10.574%	$269.4688	$269.47	$269.45	$269.50
Purchase #4	$223.31	5.706%	$236.0521	$236.05	$236.05	$236.10
Purchase #5	$38.89	4.408%	$40.6043	$40.60	$40.60	$40.60
Purchase #6	$215.45	12.404%	$242.1744	$242.17	$242.15	$242.20
Purchase #7	$38.54	6.379%	$40.9985	$41.00	$41.00	$41.00
7 purchase totals =	$1,147.09		$1,243.4936	$1,243.48	$1,243.40	$1,243.60