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	$238.95	9.586%	$261.8557	$261.86	$261.85	$261.90
Purchase #2	$63.80	6.552%	$67.9802	$67.98	$68.00	$68.00
Purchase #3	$139.46	5.650%	$147.3395	$147.34	$147.35	$147.30
Purchase #4	$132.88	13.606%	$150.9597	$150.96	$150.95	$151.00
Purchase #5	$65.41	3.852%	$67.9296	$67.93	$67.95	$67.90
Purchase #6	$150.29	12.547%	$169.1469	$169.15	$169.15	$169.10
Purchase #7	$234.73	4.749%	$245.8773	$245.88	$245.90	$245.90
7 purchase totals =	$1,025.52		$1,111.0889	$1,111.10	$1,111.15	$1,111.10