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	$155.70	4.250%	$162.3173	$162.32	$162.30	$162.30
Purchase #2	$238.97	6.120%	$253.595	$253.60	$253.60	$253.60
Purchase #3	$92.72	13.147%	$104.9099	$104.91	$104.90	$104.90
Purchase #4	$119.39	6.694%	$127.382	$127.38	$127.40	$127.40
Purchase #5	$19.40	12.868%	$21.8964	$21.90	$21.90	$21.90
Purchase #6	$58.71	3.264%	$60.6263	$60.63	$60.65	$60.60
Purchase #7	$236.33	7.251%	$253.4663	$253.47	$253.45	$253.50
7 purchase totals =	$921.22		$984.1932	$984.21	$984.20	$984.20