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	$202.50	9.327%	$221.3872	$221.39	$221.40	$221.40
Purchase #2	$135.77	5.308%	$142.9767	$142.98	$143.00	$143.00
Purchase #3	$111.29	3.278%	$114.9381	$114.94	$114.95	$114.90
Purchase #4	$201.71	10.833%	$223.5612	$223.56	$223.55	$223.60
Purchase #5	$101.65	3.183%	$104.8855	$104.89	$104.90	$104.90
Purchase #6	$211.57	9.152%	$230.9329	$230.93	$230.95	$230.90
Purchase #7	$86.95	4.469%	$90.8358	$90.84	$90.85	$90.80
7 purchase totals =	$1,051.44		$1,129.5174	$1,129.53	$1,129.60	$1,129.50