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	$119.85	3.556%	$124.1119	$124.11	$124.10	$124.10
Purchase #2	$61.54	8.636%	$66.8546	$66.85	$66.85	$66.90
Purchase #3	$207.83	4.871%	$217.9534	$217.95	$217.95	$218.00
Purchase #4	$174.66	9.319%	$190.9366	$190.94	$190.95	$190.90
Purchase #5	$167.50	10.750%	$185.5063	$185.51	$185.50	$185.50
Purchase #6	$126.59	3.745%	$131.3308	$131.33	$131.35	$131.30
Purchase #7	$155.25	3.139%	$160.1233	$160.12	$160.10	$160.10
7 purchase totals =	$1,013.22		$1,076.8169	$1,076.81	$1,076.80	$1,076.80