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	$122.37	7.197%	$131.177	$131.18	$131.20	$131.20
Purchase #2	$12.52	7.721%	$13.4867	$13.49	$13.50	$13.50
Purchase #3	$26.27	12.551%	$29.5671	$29.57	$29.55	$29.60
Purchase #4	$86.95	3.284%	$89.8054	$89.81	$89.80	$89.80
Purchase #5	$54.59	3.715%	$56.618	$56.62	$56.60	$56.60
Purchase #6	$112.76	9.684%	$123.6797	$123.68	$123.70	$123.70
Purchase #7	$43.64	5.122%	$45.8752	$45.88	$45.90	$45.90
7 purchase totals =	$459.10		$490.2091	$490.23	$490.25	$490.30