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	$119.68	7.627%	$128.808	$128.81	$128.80	$128.80
Purchase #2	$166.57	9.535%	$182.4524	$182.45	$182.45	$182.50
Purchase #3	$221.57	12.329%	$248.8874	$248.89	$248.90	$248.90
Purchase #4	$105.63	12.205%	$118.5221	$118.52	$118.50	$118.50
Purchase #5	$144.84	4.602%	$151.5055	$151.51	$151.50	$151.50
Purchase #6	$107.89	5.459%	$113.7797	$113.78	$113.80	$113.80
Purchase #7	$181.45	10.122%	$199.8164	$199.82	$199.80	$199.80
7 purchase totals =	$1,047.63		$1,143.7715	$1,143.78	$1,143.75	$1,143.80