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	$53.91	9.613%	$59.0924	$59.09	$59.10	$59.10
Purchase #2	$7.47	4.543%	$7.8094	$7.81	$7.80	$7.80
Purchase #3	$26.93	6.189%	$28.5967	$28.60	$28.60	$28.60
Purchase #4	$164.39	7.242%	$176.2951	$176.30	$176.30	$176.30
Purchase #5	$133.92	5.332%	$141.0606	$141.06	$141.05	$141.10
Purchase #6	$148.34	6.678%	$158.2461	$158.25	$158.25	$158.20
Purchase #7	$241.32	7.526%	$259.4817	$259.48	$259.50	$259.50
7 purchase totals =	$776.28		$830.5820	$830.59	$830.60	$830.60