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	$208.45	3.603%	$215.9605	$215.96	$215.95	$216.00
Purchase #2	$169.46	13.504%	$192.3439	$192.34	$192.35	$192.30
Purchase #3	$177.54	13.475%	$201.4635	$201.46	$201.45	$201.50
Purchase #4	$184.58	8.713%	$200.6625	$200.66	$200.65	$200.70
Purchase #5	$174.38	5.296%	$183.6152	$183.62	$183.60	$183.60
Purchase #6	$133.89	13.226%	$151.5983	$151.60	$151.60	$151.60
Purchase #7	$49.33	10.761%	$54.6384	$54.64	$54.65	$54.60
7 purchase totals =	$1,097.63		$1,200.2823	$1,200.28	$1,200.25	$1,200.30