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	$225.25	3.281%	$232.6405	$232.64	$232.65	$232.60
Purchase #2	$94.40	11.866%	$105.6015	$105.60	$105.60	$105.60
Purchase #3	$203.85	9.287%	$222.7815	$222.78	$222.80	$222.80
Purchase #4	$196.88	9.456%	$215.497	$215.50	$215.50	$215.50
Purchase #5	$218.64	4.381%	$228.2186	$228.22	$228.20	$228.20
Purchase #6	$94.66	9.775%	$103.913	$103.91	$103.90	$103.90
Purchase #7	$44.38	12.392%	$49.8796	$49.88	$49.90	$49.90
7 purchase totals =	$1,078.06		$1,158.5317	$1,158.53	$1,158.55	$1,158.50