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	$237.31	10.640%	$262.5598	$262.56	$262.55	$262.60
Purchase #2	$102.84	4.602%	$107.5727	$107.57	$107.55	$107.60
Purchase #3	$16.46	13.543%	$18.6892	$18.69	$18.70	$18.70
Purchase #4	$156.87	7.681%	$168.9192	$168.92	$168.90	$168.90
Purchase #5	$241.39	8.391%	$261.645	$261.65	$261.65	$261.60
Purchase #6	$107.91	3.675%	$111.8757	$111.88	$111.90	$111.90
Purchase #7	$143.25	13.203%	$162.1633	$162.16	$162.15	$162.20
7 purchase totals =	$1,006.03		$1,093.4249	$1,093.43	$1,093.40	$1,093.50