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	$59.93	8.744%	$65.1703	$65.17	$65.15	$65.20
Purchase #2	$201.90	13.365%	$228.8839	$228.88	$228.90	$228.90
Purchase #3	$47.77	9.464%	$52.291	$52.29	$52.30	$52.30
Purchase #4	$47.78	8.468%	$51.826	$51.83	$51.85	$51.80
Purchase #5	$12.30	7.580%	$13.2323	$13.23	$13.25	$13.20
Purchase #6	$11.82	4.739%	$12.3801	$12.38	$12.40	$12.40
Purchase #7	$148.54	12.394%	$166.95	$166.95	$166.95	$167.00
7 purchase totals =	$530.04		$590.7336	$590.73	$590.80	$590.80