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	$123.39	3.689%	$127.9419	$127.94	$127.95	$127.90
Purchase #2	$146.49	8.582%	$159.0618	$159.06	$159.05	$159.10
Purchase #3	$114.29	5.836%	$120.96	$120.96	$120.95	$121.00
Purchase #4	$217.43	5.292%	$228.9364	$228.94	$228.95	$228.90
Purchase #5	$146.48	12.391%	$164.6303	$164.63	$164.65	$164.60
Purchase #6	$171.38	10.672%	$189.6697	$189.67	$189.65	$189.70
Purchase #7	$101.68	3.670%	$105.4117	$105.41	$105.40	$105.40
7 purchase totals =	$1,021.14		$1,096.6118	$1,096.61	$1,096.60	$1,096.60