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	$72.52	13.857%	$82.5691	$82.57	$82.55	$82.60
Purchase #2	$240.75	3.533%	$249.2557	$249.26	$249.25	$249.30
Purchase #3	$50.85	9.420%	$55.6401	$55.64	$55.65	$55.60
Purchase #4	$61.61	6.193%	$65.4255	$65.43	$65.45	$65.40
Purchase #5	$213.31	3.689%	$221.179	$221.18	$221.20	$221.20
Purchase #6	$54.83	11.152%	$60.9446	$60.94	$60.95	$60.90
Purchase #7	$48.35	11.715%	$54.0142	$54.01	$54.00	$54.00
7 purchase totals =	$742.22		$789.0282	$789.03	$789.05	$789.00