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	$121.40	5.325%	$127.8646	$127.86	$127.85	$127.90
Purchase #2	$114.88	7.591%	$123.6005	$123.60	$123.60	$123.60
Purchase #3	$39.91	13.276%	$45.2085	$45.21	$45.20	$45.20
Purchase #4	$187.57	4.193%	$195.4348	$195.43	$195.45	$195.40
Purchase #5	$73.55	12.459%	$82.7136	$82.71	$82.70	$82.70
Purchase #6	$177.71	12.425%	$199.7905	$199.79	$199.80	$199.80
Purchase #7	$97.95	9.102%	$106.8654	$106.87	$106.85	$106.90
7 purchase totals =	$812.97		$881.4779	$881.47	$881.45	$881.50