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	$117.85	4.857%	$123.574	$123.57	$123.55	$123.60
Purchase #2	$246.31	3.545%	$255.0417	$255.04	$255.05	$255.00
Purchase #3	$185.39	6.391%	$197.2383	$197.24	$197.25	$197.20
Purchase #4	$12.70	9.168%	$13.8643	$13.86	$13.85	$13.90
Purchase #5	$88.40	4.503%	$92.3807	$92.38	$92.40	$92.40
Purchase #6	$201.95	11.381%	$224.9339	$224.93	$224.95	$224.90
Purchase #7	$73.80	5.847%	$78.1151	$78.12	$78.10	$78.10
7 purchase totals =	$926.40		$985.1480	$985.14	$985.15	$985.10