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	$78.48	4.609%	$82.0971	$82.10	$82.10	$82.10
Purchase #2	$174.94	8.627%	$190.0321	$190.03	$190.05	$190.00
Purchase #3	$78.54	3.704%	$81.4491	$81.45	$81.45	$81.40
Purchase #4	$57.62	3.290%	$59.5157	$59.52	$59.50	$59.50
Purchase #5	$152.58	9.447%	$166.9942	$166.99	$167.00	$167.00
Purchase #6	$23.37	9.753%	$25.6493	$25.65	$25.65	$25.60
Purchase #7	$56.35	8.712%	$61.2592	$61.26	$61.25	$61.30
7 purchase totals =	$621.88		$666.9967	$667.00	$667.00	$666.90