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	$31.91	4.258%	$33.2687	$33.27	$33.25	$33.30
Purchase #2	$228.65	5.544%	$241.3264	$241.33	$241.35	$241.30
Purchase #3	$70.62	8.397%	$76.55	$76.55	$76.55	$76.60
Purchase #4	$166.81	4.812%	$174.8369	$174.84	$174.85	$174.80
Purchase #5	$87.93	13.742%	$100.0133	$100.01	$100.00	$100.00
Purchase #6	$100.91	10.593%	$111.5994	$111.60	$111.60	$111.60
Purchase #7	$74.58	8.538%	$80.9476	$80.95	$80.95	$80.90
7 purchase totals =	$761.41		$818.5423	$818.55	$818.55	$818.50