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	$196.32	6.337%	$208.7608	$208.76	$208.75	$208.80
Purchase #2	$35.86	12.540%	$40.3568	$40.36	$40.35	$40.40
Purchase #3	$143.69	9.578%	$157.4526	$157.45	$157.45	$157.50
Purchase #4	$53.33	7.641%	$57.4049	$57.40	$57.40	$57.40
Purchase #5	$120.25	5.130%	$126.4188	$126.42	$126.40	$126.40
Purchase #6	$130.44	10.741%	$144.4506	$144.45	$144.45	$144.50
Purchase #7	$114.77	6.140%	$121.8169	$121.82	$121.80	$121.80
7 purchase totals =	$794.66		$856.6614	$856.66	$856.60	$856.80