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	$186.60	10.547%	$206.2807	$206.28	$206.30	$206.30
Purchase #2	$83.59	3.118%	$86.1963	$86.20	$86.20	$86.20
Purchase #3	$180.78	6.546%	$192.6139	$192.61	$192.60	$192.60
Purchase #4	$82.27	4.873%	$86.279	$86.28	$86.30	$86.30
Purchase #5	$215.28	3.838%	$223.5424	$223.54	$223.55	$223.50
Purchase #6	$129.45	12.478%	$145.6028	$145.60	$145.60	$145.60
Purchase #7	$41.93	8.338%	$45.4261	$45.43	$45.45	$45.40
7 purchase totals =	$919.90		$985.9412	$985.94	$986.00	$985.90