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	$231.51	13.814%	$263.4908	$263.49	$263.50	$263.50
Purchase #2	$177.31	12.473%	$199.4259	$199.43	$199.45	$199.40
Purchase #3	$176.45	13.749%	$200.7101	$200.71	$200.70	$200.70
Purchase #4	$106.49	9.810%	$116.9367	$116.94	$116.95	$116.90
Purchase #5	$177.67	12.303%	$199.5287	$199.53	$199.55	$199.50
Purchase #6	$235.79	4.580%	$246.5892	$246.59	$246.60	$246.60
Purchase #7	$174.69	12.616%	$196.7289	$196.73	$196.75	$196.70
7 purchase totals =	$1,279.91		$1,423.4103	$1,423.42	$1,423.50	$1,423.30