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	$182.96	12.296%	$205.4568	$205.46	$205.45	$205.50
Purchase #2	$146.43	6.679%	$156.2101	$156.21	$156.20	$156.20
Purchase #3	$243.90	6.261%	$259.1706	$259.17	$259.15	$259.20
Purchase #4	$69.71	4.814%	$73.0658	$73.07	$73.05	$73.10
Purchase #5	$236.97	9.493%	$259.4656	$259.47	$259.45	$259.50
Purchase #6	$40.47	4.546%	$42.3098	$42.31	$42.30	$42.30
Purchase #7	$176.37	11.544%	$196.7302	$196.73	$196.75	$196.70
7 purchase totals =	$1,096.81		$1,192.4089	$1,192.42	$1,192.35	$1,192.50