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	$156.61	11.686%	$174.9114	$174.91	$174.90	$174.90
Purchase #2	$198.95	9.533%	$217.9159	$217.92	$217.90	$217.90
Purchase #3	$200.95	7.182%	$215.3822	$215.38	$215.40	$215.40
Purchase #4	$129.75	11.667%	$144.8879	$144.89	$144.90	$144.90
Purchase #5	$195.51	6.778%	$208.7617	$208.76	$208.75	$208.80
Purchase #6	$107.78	12.195%	$120.9238	$120.92	$120.90	$120.90
Purchase #7	$246.63	9.714%	$270.5876	$270.59	$270.60	$270.60
7 purchase totals =	$1,236.18		$1,353.3705	$1,353.37	$1,353.35	$1,353.40