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	$109.38	9.554%	$119.8302	$119.83	$119.85	$119.80
Purchase #2	$192.35	5.458%	$202.8485	$202.85	$202.85	$202.80
Purchase #3	$69.34	4.768%	$72.6461	$72.65	$72.65	$72.60
Purchase #4	$99.88	11.144%	$111.0106	$111.01	$111.00	$111.00
Purchase #5	$114.95	5.562%	$121.3435	$121.34	$121.35	$121.30
Purchase #6	$203.29	4.333%	$212.0986	$212.10	$212.10	$212.10
Purchase #7	$88.65	13.817%	$100.8988	$100.90	$100.90	$100.90
7 purchase totals =	$877.84		$940.6763	$940.68	$940.70	$940.50