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	$179.95	6.746%	$192.0894	$192.09	$192.10	$192.10
Purchase #2	$147.30	11.625%	$164.4236	$164.42	$164.40	$164.40
Purchase #3	$53.97	10.258%	$59.5062	$59.51	$59.50	$59.50
Purchase #4	$130.25	9.521%	$142.6511	$142.65	$142.65	$142.70
Purchase #5	$215.41	3.161%	$222.2191	$222.22	$222.20	$222.20
Purchase #6	$89.81	11.847%	$100.4498	$100.45	$100.45	$100.40
Purchase #7	$60.81	5.163%	$63.9496	$63.95	$63.95	$63.90
7 purchase totals =	$877.50		$945.2888	$945.29	$945.25	$945.20