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	$76.40	9.426%	$83.6015	$83.60	$83.60	$83.60
Purchase #2	$187.89	9.622%	$205.9688	$205.97	$205.95	$206.00
Purchase #3	$207.69	12.560%	$233.7759	$233.78	$233.80	$233.80
Purchase #4	$241.46	9.696%	$264.872	$264.87	$264.85	$264.90
Purchase #5	$229.30	13.789%	$260.9182	$260.92	$260.90	$260.90
Purchase #6	$63.82	3.622%	$66.1316	$66.13	$66.15	$66.10
Purchase #7	$51.66	3.680%	$53.5611	$53.56	$53.55	$53.60
7 purchase totals =	$1,058.22		$1,168.8291	$1,168.83	$1,168.80	$1,168.90