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	$102.27	12.545%	$115.0998	$115.10	$115.10	$115.10
Purchase #2	$174.41	12.610%	$196.4031	$196.40	$196.40	$196.40
Purchase #3	$37.64	5.226%	$39.6071	$39.61	$39.60	$39.60
Purchase #4	$84.63	5.678%	$89.4353	$89.44	$89.45	$89.40
Purchase #5	$123.44	7.493%	$132.6894	$132.69	$132.70	$132.70
Purchase #6	$209.95	13.128%	$237.5122	$237.51	$237.50	$237.50
Purchase #7	$184.88	4.264%	$192.7633	$192.76	$192.75	$192.80
7 purchase totals =	$917.22		$1,003.5102	$1,003.51	$1,003.50	$1,003.50