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	$72.69	8.306%	$78.7276	$78.73	$78.75	$78.70
Purchase #2	$214.27	13.298%	$242.7636	$242.76	$242.75	$242.80
Purchase #3	$177.64	10.455%	$196.2123	$196.21	$196.20	$196.20
Purchase #4	$214.53	3.762%	$222.6006	$222.60	$222.60	$222.60
Purchase #5	$144.29	4.517%	$150.8076	$150.81	$150.80	$150.80
Purchase #6	$126.80	4.783%	$132.8648	$132.86	$132.85	$132.90
Purchase #7	$125.75	3.737%	$130.4493	$130.45	$130.45	$130.40
7 purchase totals =	$1,075.97		$1,154.4258	$1,154.42	$1,154.40	$1,154.40