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	$228.59	5.696%	$241.6105	$241.61	$241.60	$241.60
Purchase #2	$247.97	13.824%	$282.2494	$282.25	$282.25	$282.20
Purchase #3	$71.83	9.441%	$78.6115	$78.61	$78.60	$78.60
Purchase #4	$181.64	13.383%	$205.9489	$205.95	$205.95	$205.90
Purchase #5	$113.53	4.332%	$118.4481	$118.45	$118.45	$118.40
Purchase #6	$242.84	8.267%	$262.9156	$262.92	$262.90	$262.90
Purchase #7	$107.80	4.252%	$112.3837	$112.38	$112.40	$112.40
7 purchase totals =	$1,194.20		$1,302.1677	$1,302.17	$1,302.15	$1,302.00