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	$123.63	7.307%	$132.6636	$132.66	$132.65	$132.70
Purchase #2	$162.78	3.153%	$167.9125	$167.91	$167.90	$167.90
Purchase #3	$144.98	3.759%	$150.4298	$150.43	$150.45	$150.40
Purchase #4	$52.94	6.422%	$56.3398	$56.34	$56.35	$56.30
Purchase #5	$225.85	6.533%	$240.6048	$240.60	$240.60	$240.60
Purchase #6	$144.32	9.597%	$158.1704	$158.17	$158.15	$158.20
Purchase #7	$53.87	5.811%	$57.0004	$57.00	$57.00	$57.00
7 purchase totals =	$908.37		$963.1213	$963.11	$963.10	$963.10