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	$215.59	7.381%	$231.5027	$231.50	$231.50	$231.50
Purchase #2	$180.86	5.182%	$190.2322	$190.23	$190.25	$190.20
Purchase #3	$158.51	5.583%	$167.3596	$167.36	$167.35	$167.40
Purchase #4	$24.44	13.309%	$27.6927	$27.69	$27.70	$27.70
Purchase #5	$34.36	9.453%	$37.6081	$37.61	$37.60	$37.60
Purchase #6	$186.40	5.654%	$196.9391	$196.94	$196.95	$196.90
Purchase #7	$128.42	3.767%	$133.2576	$133.26	$133.25	$133.30
7 purchase totals =	$928.58		$984.5920	$984.59	$984.60	$984.60