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	$125.69	8.787%	$136.7344	$136.73	$136.75	$136.70
Purchase #2	$37.60	11.271%	$41.8379	$41.84	$41.85	$41.80
Purchase #3	$205.68	9.719%	$225.67	$225.67	$225.65	$225.70
Purchase #4	$54.35	9.623%	$59.5801	$59.58	$59.60	$59.60
Purchase #5	$182.33	8.438%	$197.715	$197.72	$197.70	$197.70
Purchase #6	$52.66	4.237%	$54.8912	$54.89	$54.90	$54.90
Purchase #7	$40.40	11.645%	$45.1046	$45.10	$45.10	$45.10
7 purchase totals =	$698.71		$761.5332	$761.53	$761.55	$761.50