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	$208.43	4.403%	$217.6072	$217.61	$217.60	$217.60
Purchase #2	$149.77	11.857%	$167.5282	$167.53	$167.55	$167.50
Purchase #3	$84.66	6.767%	$90.3889	$90.39	$90.40	$90.40
Purchase #4	$51.73	3.322%	$53.4485	$53.45	$53.45	$53.40
Purchase #5	$106.31	12.811%	$119.9294	$119.93	$119.95	$119.90
Purchase #6	$196.87	12.834%	$222.1363	$222.14	$222.15	$222.10
Purchase #7	$142.89	12.611%	$160.9099	$160.91	$160.90	$160.90
7 purchase totals =	$940.66		$1,031.9484	$1,031.96	$1,032.00	$1,031.80