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	$166.61	10.724%	$184.4773	$184.48	$184.50	$184.50
Purchase #2	$101.88	3.443%	$105.3877	$105.39	$105.40	$105.40
Purchase #3	$232.81	5.230%	$244.986	$244.99	$245.00	$245.00
Purchase #4	$165.65	11.426%	$184.5772	$184.58	$184.60	$184.60
Purchase #5	$158.43	10.230%	$174.6374	$174.64	$174.65	$174.60
Purchase #6	$168.38	4.212%	$175.4722	$175.47	$175.45	$175.50
Purchase #7	$34.89	3.514%	$36.116	$36.12	$36.10	$36.10
7 purchase totals =	$1,028.65		$1,105.6538	$1,105.67	$1,105.70	$1,105.70