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	$160.62	4.297%	$167.5218	$167.52	$167.50	$167.50
Purchase #2	$102.86	8.362%	$111.4612	$111.46	$111.45	$111.50
Purchase #3	$139.69	8.366%	$151.3765	$151.38	$151.40	$151.40
Purchase #4	$47.89	8.466%	$51.9444	$51.94	$51.95	$51.90
Purchase #5	$208.61	3.822%	$216.5831	$216.58	$216.60	$216.60
Purchase #6	$50.75	5.405%	$53.493	$53.49	$53.50	$53.50
Purchase #7	$100.62	3.279%	$103.9193	$103.92	$103.90	$103.90
7 purchase totals =	$811.04		$856.2993	$856.29	$856.30	$856.30