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	$234.51	10.650%	$259.4853	$259.49	$259.50	$259.50
Purchase #2	$142.75	10.751%	$158.0971	$158.10	$158.10	$158.10
Purchase #3	$167.46	9.428%	$183.2481	$183.25	$183.25	$183.20
Purchase #4	$37.60	8.839%	$40.9235	$40.92	$40.90	$40.90
Purchase #5	$100.27	7.603%	$107.8935	$107.89	$107.90	$107.90
Purchase #6	$113.86	8.851%	$123.9377	$123.94	$123.95	$123.90
Purchase #7	$232.79	11.456%	$259.4584	$259.46	$259.45	$259.50
7 purchase totals =	$1,029.24		$1,133.0436	$1,133.05	$1,133.05	$1,133.00