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	$84.95	4.259%	$88.568	$88.57	$88.55	$88.60
Purchase #2	$107.81	9.867%	$118.4476	$118.45	$118.45	$118.40
Purchase #3	$119.35	9.767%	$131.0069	$131.01	$131.00	$131.00
Purchase #4	$34.60	8.812%	$37.649	$37.65	$37.65	$37.60
Purchase #5	$230.50	12.407%	$259.0981	$259.10	$259.10	$259.10
Purchase #6	$86.83	4.109%	$90.3978	$90.40	$90.40	$90.40
Purchase #7	$237.61	5.446%	$250.5502	$250.55	$250.55	$250.60
7 purchase totals =	$901.65		$975.7176	$975.73	$975.70	$975.70