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	$219.43	8.521%	$238.1276	$238.13	$238.15	$238.10
Purchase #2	$19.34	12.472%	$21.7521	$21.75	$21.75	$21.80
Purchase #3	$19.66	10.328%	$21.6905	$21.69	$21.70	$21.70
Purchase #4	$145.61	3.202%	$150.2724	$150.27	$150.25	$150.30
Purchase #5	$40.42	9.393%	$44.2167	$44.22	$44.20	$44.20
Purchase #6	$31.34	3.605%	$32.4698	$32.47	$32.45	$32.50
Purchase #7	$166.66	11.357%	$185.5876	$185.59	$185.60	$185.60
7 purchase totals =	$642.46		$694.1167	$694.12	$694.10	$694.20