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	$40.81	12.545%	$45.9296	$45.93	$45.95	$45.90
Purchase #2	$12.40	5.716%	$13.1088	$13.11	$13.10	$13.10
Purchase #3	$107.70	13.308%	$122.0327	$122.03	$122.05	$122.00
Purchase #4	$46.42	8.827%	$50.5175	$50.52	$50.50	$50.50
Purchase #5	$20.40	3.739%	$21.1628	$21.16	$21.15	$21.20
Purchase #6	$123.93	13.272%	$140.378	$140.38	$140.40	$140.40
Purchase #7	$59.78	13.392%	$67.7857	$67.79	$67.80	$67.80
7 purchase totals =	$411.44		$460.9151	$460.92	$460.95	$460.90