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	$56.88	4.693%	$59.5494	$59.55	$59.55	$59.50
Purchase #2	$182.46	6.578%	$194.4622	$194.46	$194.45	$194.50
Purchase #3	$183.57	9.580%	$201.156	$201.16	$201.15	$201.20
Purchase #4	$221.64	11.676%	$247.5187	$247.52	$247.50	$247.50
Purchase #5	$21.53	13.201%	$24.3722	$24.37	$24.35	$24.40
Purchase #6	$167.57	6.492%	$178.4486	$178.45	$178.45	$178.40
Purchase #7	$164.78	4.782%	$172.6598	$172.66	$172.65	$172.70
7 purchase totals =	$998.43		$1,078.1669	$1,078.17	$1,078.10	$1,078.20