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	$168.95	12.660%	$190.3391	$190.34	$190.35	$190.30
Purchase #2	$156.28	11.724%	$174.6023	$174.60	$174.60	$174.60
Purchase #3	$61.61	5.832%	$65.2031	$65.20	$65.20	$65.20
Purchase #4	$181.41	10.541%	$200.5324	$200.53	$200.55	$200.50
Purchase #5	$140.68	11.703%	$157.1438	$157.14	$157.15	$157.10
Purchase #6	$52.71	6.661%	$56.221	$56.22	$56.20	$56.20
Purchase #7	$178.79	9.691%	$196.1165	$196.12	$196.10	$196.10
7 purchase totals =	$940.43		$1,040.1582	$1,040.15	$1,040.15	$1,040.00