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	$213.40	11.634%	$238.227	$238.23	$238.25	$238.20
Purchase #2	$146.76	12.373%	$164.9186	$164.92	$164.90	$164.90
Purchase #3	$207.28	9.461%	$226.8908	$226.89	$226.90	$226.90
Purchase #4	$38.62	4.287%	$40.2756	$40.28	$40.30	$40.30
Purchase #5	$168.64	5.109%	$177.2558	$177.26	$177.25	$177.30
Purchase #6	$87.86	7.657%	$94.5874	$94.59	$94.60	$94.60
Purchase #7	$130.89	9.847%	$143.7787	$143.78	$143.80	$143.80
7 purchase totals =	$993.45		$1,085.9339	$1,085.95	$1,086.00	$1,086.00