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	$200.85	13.602%	$228.1696	$228.17	$228.15	$228.20
Purchase #2	$38.29	12.723%	$43.1616	$43.16	$43.15	$43.20
Purchase #3	$19.41	7.455%	$20.857	$20.86	$20.85	$20.90
Purchase #4	$208.97	4.307%	$217.9703	$217.97	$217.95	$218.00
Purchase #5	$55.88	5.278%	$58.8293	$58.83	$58.85	$58.80
Purchase #6	$54.54	8.607%	$59.2343	$59.23	$59.25	$59.20
Purchase #7	$66.39	7.830%	$71.5883	$71.59	$71.60	$71.60
7 purchase totals =	$644.33		$699.8104	$699.81	$699.80	$699.90