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	$107.36	3.838%	$111.4805	$111.48	$111.50	$111.50
Purchase #2	$78.44	3.628%	$81.2858	$81.29	$81.30	$81.30
Purchase #3	$172.42	10.152%	$189.9241	$189.92	$189.90	$189.90
Purchase #4	$8.51	9.692%	$9.3348	$9.33	$9.35	$9.30
Purchase #5	$196.48	5.272%	$206.8384	$206.84	$206.85	$206.80
Purchase #6	$70.49	11.566%	$78.6429	$78.64	$78.65	$78.60
Purchase #7	$241.90	5.710%	$255.7125	$255.71	$255.70	$255.70
7 purchase totals =	$875.60		$933.2190	$933.21	$933.25	$933.10