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	$184.75	6.617%	$196.9749	$196.97	$196.95	$197.00
Purchase #2	$105.37	8.541%	$114.3697	$114.37	$114.35	$114.40
Purchase #3	$183.62	13.645%	$208.6749	$208.67	$208.65	$208.70
Purchase #4	$98.86	12.695%	$111.4103	$111.41	$111.40	$111.40
Purchase #5	$151.35	9.854%	$166.264	$166.26	$166.25	$166.30
Purchase #6	$19.32	11.799%	$21.5996	$21.60	$21.60	$21.60
Purchase #7	$132.26	9.762%	$145.1712	$145.17	$145.15	$145.20
7 purchase totals =	$875.53		$964.4646	$964.45	$964.35	$964.60