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	$178.87	9.806%	$196.41	$196.41	$196.40	$196.40
Purchase #2	$126.76	4.458%	$132.411	$132.41	$132.40	$132.40
Purchase #3	$54.97	13.169%	$62.209	$62.21	$62.20	$62.20
Purchase #4	$171.82	3.315%	$177.5158	$177.52	$177.50	$177.50
Purchase #5	$81.87	8.640%	$88.9436	$88.94	$88.95	$88.90
Purchase #6	$242.47	5.339%	$255.4155	$255.42	$255.40	$255.40
Purchase #7	$26.69	7.814%	$28.7756	$28.78	$28.80	$28.80
7 purchase totals =	$883.45		$941.6805	$941.69	$941.65	$941.60