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	$117.83	7.786%	$127.0042	$127.00	$127.00	$127.00
Purchase #2	$182.49	3.615%	$189.087	$189.09	$189.10	$189.10
Purchase #3	$49.48	7.248%	$53.0663	$53.07	$53.05	$53.10
Purchase #4	$201.82	4.246%	$210.3893	$210.39	$210.40	$210.40
Purchase #5	$131.77	4.573%	$137.7958	$137.80	$137.80	$137.80
Purchase #6	$73.40	12.533%	$82.5992	$82.60	$82.60	$82.60
Purchase #7	$124.43	5.162%	$130.8531	$130.85	$130.85	$130.90
7 purchase totals =	$881.22		$930.7949	$930.80	$930.80	$930.90