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	$164.82	13.751%	$187.4844	$187.48	$187.50	$187.50
Purchase #2	$40.93	4.267%	$42.6765	$42.68	$42.70	$42.70
Purchase #3	$51.87	10.414%	$57.2717	$57.27	$57.25	$57.30
Purchase #4	$127.78	3.808%	$132.6459	$132.65	$132.65	$132.60
Purchase #5	$207.52	7.417%	$222.9118	$222.91	$222.90	$222.90
Purchase #6	$235.61	9.691%	$258.443	$258.44	$258.45	$258.40
Purchase #7	$250.25	6.474%	$266.4512	$266.45	$266.45	$266.50
7 purchase totals =	$1,078.78		$1,167.8845	$1,167.88	$1,167.90	$1,167.90