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	$149.40	8.819%	$162.5756	$162.58	$162.60	$162.60
Purchase #2	$156.26	10.110%	$172.0579	$172.06	$172.05	$172.10
Purchase #3	$67.94	5.337%	$71.566	$71.57	$71.55	$71.60
Purchase #4	$199.91	13.808%	$227.5136	$227.51	$227.50	$227.50
Purchase #5	$125.39	9.287%	$137.035	$137.04	$137.05	$137.00
Purchase #6	$121.81	4.586%	$127.3962	$127.40	$127.40	$127.40
Purchase #7	$43.81	8.181%	$47.3941	$47.39	$47.40	$47.40
7 purchase totals =	$864.52		$945.5384	$945.55	$945.55	$945.60