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	$9.96	9.197%	$10.876	$10.88	$10.90	$10.90
Purchase #2	$241.70	5.761%	$255.6243	$255.62	$255.60	$255.60
Purchase #3	$17.50	9.308%	$19.1289	$19.13	$19.15	$19.10
Purchase #4	$160.77	13.443%	$182.3823	$182.38	$182.40	$182.40
Purchase #5	$159.39	9.801%	$175.0118	$175.01	$175.00	$175.00
Purchase #6	$155.59	10.247%	$171.5333	$171.53	$171.55	$171.50
Purchase #7	$170.41	13.214%	$192.928	$192.93	$192.95	$192.90
7 purchase totals =	$915.32		$1,007.4846	$1,007.48	$1,007.55	$1,007.40