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	$123.43	10.571%	$136.4778	$136.48	$136.50	$136.50
Purchase #2	$208.89	11.180%	$232.2439	$232.24	$232.25	$232.20
Purchase #3	$217.75	8.760%	$236.8249	$236.82	$236.80	$236.80
Purchase #4	$107.61	4.458%	$112.4073	$112.41	$112.40	$112.40
Purchase #5	$40.40	5.385%	$42.5755	$42.58	$42.60	$42.60
Purchase #6	$133.39	7.429%	$143.2995	$143.30	$143.30	$143.30
Purchase #7	$199.75	11.571%	$222.8631	$222.86	$222.85	$222.90
7 purchase totals =	$1,031.22		$1,126.6920	$1,126.69	$1,126.70	$1,126.70