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	$192.78	10.695%	$213.3978	$213.40	$213.40	$213.40
Purchase #2	$32.70	12.811%	$36.8892	$36.89	$36.90	$36.90
Purchase #3	$184.78	11.726%	$206.4473	$206.45	$206.45	$206.40
Purchase #4	$152.90	7.749%	$164.7482	$164.75	$164.75	$164.70
Purchase #5	$161.38	7.135%	$172.8945	$172.89	$172.90	$172.90
Purchase #6	$230.48	5.206%	$242.4788	$242.48	$242.50	$242.50
Purchase #7	$12.44	3.612%	$12.8893	$12.89	$12.90	$12.90
7 purchase totals =	$967.46		$1,049.7451	$1,049.75	$1,049.80	$1,049.70