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	$235.47	11.580%	$262.7374	$262.74	$262.75	$262.70
Purchase #2	$221.83	4.555%	$231.9344	$231.93	$231.95	$231.90
Purchase #3	$44.92	6.695%	$47.9274	$47.93	$47.95	$47.90
Purchase #4	$237.88	12.107%	$266.6801	$266.68	$266.70	$266.70
Purchase #5	$57.37	3.386%	$59.3125	$59.31	$59.30	$59.30
Purchase #6	$70.90	11.267%	$78.8883	$78.89	$78.90	$78.90
Purchase #7	$29.97	8.417%	$32.4926	$32.49	$32.50	$32.50
7 purchase totals =	$898.34		$979.9727	$979.97	$980.05	$979.90