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	$159.83	5.636%	$168.838	$168.84	$168.85	$168.80
Purchase #2	$132.25	5.769%	$139.8795	$139.88	$139.90	$139.90
Purchase #3	$85.87	12.105%	$96.2646	$96.26	$96.25	$96.30
Purchase #4	$137.83	3.713%	$142.9476	$142.95	$142.95	$142.90
Purchase #5	$142.56	12.613%	$160.5411	$160.54	$160.55	$160.50
Purchase #6	$150.82	10.106%	$166.0619	$166.06	$166.05	$166.10
Purchase #7	$99.40	9.228%	$108.5726	$108.57	$108.55	$108.60
7 purchase totals =	$908.56		$983.1053	$983.10	$983.10	$983.10