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	$104.73	13.181%	$118.5345	$118.53	$118.55	$118.50
Purchase #2	$51.82	3.299%	$53.5295	$53.53	$53.55	$53.50
Purchase #3	$105.76	5.384%	$111.4541	$111.45	$111.45	$111.50
Purchase #4	$115.31	12.313%	$129.5081	$129.51	$129.50	$129.50
Purchase #5	$137.71	5.285%	$144.988	$144.99	$145.00	$145.00
Purchase #6	$124.58	12.499%	$140.1513	$140.15	$140.15	$140.20
Purchase #7	$156.31	3.861%	$162.3451	$162.35	$162.35	$162.30
7 purchase totals =	$796.22		$860.5106	$860.51	$860.55	$860.50