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	$82.85	9.459%	$90.6868	$90.69	$90.70	$90.70
Purchase #2	$102.52	10.158%	$112.934	$112.93	$112.95	$112.90
Purchase #3	$11.50	12.616%	$12.9508	$12.95	$12.95	$13.00
Purchase #4	$237.95	6.516%	$253.4548	$253.45	$253.45	$253.50
Purchase #5	$236.32	4.680%	$247.3798	$247.38	$247.40	$247.40
Purchase #6	$118.82	10.273%	$131.0264	$131.03	$131.05	$131.00
Purchase #7	$232.61	11.457%	$259.2601	$259.26	$259.25	$259.30
7 purchase totals =	$1,022.57		$1,107.6927	$1,107.69	$1,107.75	$1,107.80